Keywords To Remember
- Electric charge
The property of matter that causes it to experience a force when placed in an electric and magnetic field. Objects that attract light objects after rubbing are said to have an electric charge. - Electricity
A form of energy resulting from the existence of charged particles such as electrons or protons. - Electric current
The flow of electric charge through a conductor, usually measured in amperes. - Insulator
A material that does not allow electric charges to flow through it easily. - Conductor
A material that allows electric charges to pass through it easily. - Charging by friction (rubbing)
The process of making an object electrically charged by rubbing it with another object. - Charging by conduction (contact)
The process of charging an uncharged object by touching it with a charged object, so the charge gets transferred. - Charging by induction
The process of charging an object without direct contact, by bringing a charged object near it and using earthing. - Earthing (grounding)
Connecting a charged object to the Earth to allow excess charge to flow away, making the object neutral. - Electric induction
The phenomenon where an uncharged object’s charges separate due to the presence of a nearby charged object. - Like charges
Charges that are the same in nature (both positive or both negative) which repel each other. - Unlike charges
Charges that are opposite in nature (one positive and one negative) which attract each other. - Positive charge
A type of electric charge, defined by Benjamin Franklin, typically found on a glass rod rubbed with silk. - Negative charge
A type of electric charge, typically found on an ebonite rod rubbed with flannel. - Electric discharge
A sudden flow of electric charge through a medium like air, causing lightning or sparks. - Lightning
A natural electric discharge of very high voltage between clouds or between clouds and the ground, accompanied by light and thunder. - Thunder
The sound caused by the rapid expansion of air heated by a lightning discharge. - Lightning conductor
A device made of metal, installed on buildings, to safely direct lightning charges into the ground to prevent damage. - Gold leaf electroscope
A device used to detect the presence and amount of electric charge on an object. - Electric motor
A device that converts electrical energy into mechanical energy, commonly used in household appliances and industry. - Uninterrupted Power Supply (UPS)
A device that provides emergency power to electrical equipment when the main power fails. - Electric bulb
A device that produces light when electricity passes through it. - Refrigerator
An appliance that uses electricity to keep food cold and fresh. - Electric fan
A device that creates airflow for cooling using electric power. - Electric pump
A device that uses electricity to move fluids like water, often used in irrigation.
Something To Know
A. Fill in the blanks.
- There are __________ types of charges in nature.
Answer – two
- __________ charges repel each other and unlike charges __________ each other.
Answer – Like, attract
- The materials, that normally do not get __________ on rubbing, and allow electric current to flow through them with ease, are known as __________
Answer – charged, conductors
- Lightning and__________ occur together.
Answer – thunder
- The scientist, who proved that lightning is electrical in nature, was __________ .
Answer – Benjamin Franklin
B. Write True or False for the following statements.
- The charges acquired by a glass rod, and the silk cloth with which it is rubbed, are equal and of the same sign.
Answer – False
- During charging by conduction, the charged object shares its charge with the uncharged object.
Answer – True
- A charged body loses its charge if we touch it with our hand.
Answer – True
Lightning is a natural electrical discharge phenomenon.
Answer – True
- We do not need any special device to protect tall buildings from lightning.
Answer – False
C. Tick (✓) the correct option.
- A charged plastic comb (comb B) is brought near another similarly charged, and suspended, plastic comb (comb A). Then comb A would—
remain unaffected
move away from comb B
move towards comb B
start oscillating
Answer – move away from comb B
- A student is provided with four objects:
A: A plastic comb
B: A rubber balloon
C: A copper rod
D: A woolen cloth
The object, that cannot be easily charged by rubbing, is the object labelled as—
A
B
C
D
Answer – C
- Two charged objects, are brought close to each other. The two objects would—
always repel each other.
always attract each other.
either attract or repel each other.
neither attract nor repel each other.
Answer – either attract or repel each other.
- During charging, by induction, it is—
the charged object, as well as the earth, that share their charges with the object to be charged.
only the charged object that shares its charges, with the object to be charged,
only the earth that ‘shares its charges’, with the object to be charged.
the uncharged object that is able to produce charges on itself.
Answer – the uncharged object that is able to produce charges on itself.
- During charging (i) by conduction, and (ii) by induction, the charge on the charging object-
decreases in both the cases.
decreases in the first case but remains unchanged in the second case.
decreases in the second case but remains unchanged in the first case.
remains unchanged in both the cases.
Answer – decreases in the first case but remains unchanged in the second case.
- During lightning, we can have an electric discharge-
only between two opposite charged clouds,
only between a charged cloud and the ground,
either between two opposite charged clouds or between a charged cloud and the ground.
neither between two opposite charged clouds nor between a charged cloud and the ground.
Answer – either between two opposite charged clouds or between a charged cloud and the ground.
D. Answer the following questions in brief.
- A glass rod is rubbed against a silk cloth. Which object/s gets/get charged in this process?
Answer – Both the glass rod and the silk cloth get charged; the glass rod becomes positively charged, and the silk cloth becomes negatively charged.
- Name two objects (a) that can be charged by rubbing (b) that do not get charged on rubbing.
Answer – (a) Glass rod, plastic comb
(b) Copper rod, iron rod
- State the main difference between a conductor and an insulator.
Answer – Conductors allow electric charges to flow easily, while insulators do not allow charges to flow easily.
- Name the device used for protecting tall buildings from lightning strikes.
Answer – Lightning conductor
- Give the meaning of the term ‘earthing’.
Answer – Earthing is the process of connecting a charged object to the earth to remove excess charge and make it neutral.
- List down two precautions that a person can take if he is caught outside in the open during a lightning strike.
Answer – Avoid standing near tall trees or metal objects.
Crouch down and keep your feet close together without lying flat on the ground.
E. Answer the following questions
- A charged drinking plastic straw is brought near another suspended plastic straw, that is (a) similarly charged (b) uncharged. Explain what we would observe in each case and why.
Answer – (a) The similarly charged straw will repel the suspended straw because like charges repel.
(b) The uncharged straw will be attracted to the charged straw because the charged straw induces opposite charges on the uncharged straw, causing attraction.
- Why do we say that ‘charges are always produced in pairs’?
Answer – Because when an object gains electrons and becomes negatively charged, another object loses electrons and becomes positively charged, so charges are always created in equal and opposite amounts.
- Describe a simple experiment to show that the total charge on a pair of objects, that have been rubbed together, is zero.
Answer – Rub a glass rod with a silk cloth. Both become charged with opposite charges. Using an electroscope, test the charges and see they are equal and opposite, confirming the total charge is zero.
- Why does a charged object lose its charge when touched?
Answer – Because the charge flows away to the earth or the person touching it, neutralizing the charge on the object.
- Can we say that a charged object attracts an uncharged object by first charging it through induction? Explain your answer.
Answer – Yes, because the charged object causes separation of charges in the uncharged object, inducing a charge that results in attraction.
- State the sign of the charge acquired by an object when it is charged, by a positively charged rod, through (a) conduction (b) induction. Give the reason for your statement.
Answer – (a) Positive — because in conduction, the charge is transferred directly from the rod.
(b) Negative — because induction causes opposite charges to gather near the rod.
- Is it important to have a very good contact between the lower end of a lightning conductor and the earth? If so, why?
Answer – Yes, to ensure that the electric charge from lightning is safely conducted into the ground without causing damage.
Value Based Question
Tavish was driving back home from his office when it started raining heavily. The rain poured along with a thundering sound and lightning. On the way he saw an old man walking along the street. Tavish stopped the car and requested him to immediately get inside the car. Later on, he dropped the old man at his place.
- State two values displayed by Tavish.
Answer – Compassion and responsibility
- Did Tavish do the right thing by asking the old man to get inside his car? Give reason for your answer.
Answer – Yes, because he ensured the old man’s safety from lightning and rain, showing kindness and concern for others.
Something To Do
- To design a simple metal leaf electroscope.
We can design a simple version of a gold leaf electroscope by using—
(i) an aluminium leaf
(ii) a wooden stand
(iii) a metal wire and
(iv) a ‘box’ made from thermocole sheets with transparent paper walls.
We can use it for applications similar to that of a gold leaf electroscope.
Answer – Yes, by using an aluminium leaf, a wooden stand, a metal wire, and a box made from thermocole sheets with transparent paper walls, we can make a simple electroscope to detect electric charge.
- Solve the crossword with the help of given clues.
Across —
- Charging by rubbing.
- A natural electrical discharge phenomenon.
- A positive charge gets attracted by a _______charge.
- Loud sound.
Down
- Transfer of charge from one object to another.
- Charging an object without touching it.
- Charging by making contact.
- Transfer of charge to earth.
Answer – Across —
Charging by rubbing. — Friction
A natural electrical discharge phenomenon. — Lightning
A positive charge gets attracted by a _______charge. — Negative
Loud sound. — Thunder
Down —
- Transfer of charge from one object to another. — Conduction
- Charging an object without touching it. — Induction
- Charging by making contact. — Conduction
- Transfer of charge to earth. — Earthing
Additional Questions and Answers – 01
Fill in the blanks (with answers)
- Electric charge is measured in __________.
Answer: coulombs - When two objects are rubbed together, electrons are transferred from one to the other, causing __________ charging.
Answer: frictional - The unit of electric current is __________.
Answer: ampere - An object with equal numbers of positive and negative charges is said to be __________.
Answer: neutral - A positively charged object has __________ electrons than protons.
Answer: fewer - The device used to detect electric charge is called an __________.
Answer: electroscope - When a charged object loses its charge by touching the ground, the process is called __________.
Answer: earthing - __________ is the force experienced between two charged objects.
Answer: Electrostatic force
Multiple Choice Questions (MCQs) (with answers)
- What happens when a positively charged rod is brought near a neutral metal sphere?
a) The sphere becomes positively charged
b) The sphere becomes negatively charged by induction
c) The sphere repels the rod
d) Nothing happens
Answer: b) The sphere becomes negatively charged by induction - Which of the following materials is a good conductor?
a) Rubber
b) Copper
c) Plastic
d) Glass
Answer: b) Copper - Which scientist is credited with the discovery of the law of electric charges?
a) Isaac Newton
b) Benjamin Franklin
c) Charles Coulomb
d) Michael Faraday
Answer: c) Charles Coulomb - During frictional charging, the object that loses electrons becomes —
a) Negatively charged
b) Positively charged
c) Neutral
d) Unaffected
Answer: b) Positively charged - What is the main purpose of a lightning conductor?
a) To attract lightning
b) To prevent the formation of lightning
c) To safely conduct lightning to the earth
d) To produce electricity from lightning
Answer: c) To safely conduct lightning to the earth
True/False Questions (with answers)
- Charging by conduction involves direct contact between objects.
Answer: True - Like charges always attract each other.
Answer: False - Conductors do not allow the flow of electric current.
Answer: False - The charge on an electron is negative.
Answer: True - Lightning is a man-made phenomenon.
Answer: False - A rubber balloon can be charged by rubbing it against wool.
Answer: True - When a charged object is connected to the earth, it becomes neutral.
Answer: True
Short Questions and Answers
- What is an insulator?
Answer: An insulator is a material that does not allow electric charges to flow through it easily. - Define electric charge.
Answer: Electric charge is a physical property of matter that causes it to experience a force in an electric field. - Name two materials that can be charged by rubbing.
Answer: Plastic comb and glass rod. - What is the role of electrons in electric charge?
Answer: Electrons carry negative charge and their movement causes electric current. - Why does a charged body attract an uncharged body?
Answer: Because it induces opposite charges on the uncharged body, causing attraction. - What safety measure is used in buildings to protect them from lightning?
Answer: Lightning conductor.
Competency Based Questions (Reasoning and Assertion-Reason type)
- Assertion (A): Like charges repel each other.
Reason (R): Because like charges have the same type of electric force.
Answer: Both A and R are true, and R is the correct explanation of A. - Assertion (A): A conductor cannot be charged by induction.
Reason (R): Induction requires contact between objects.
Answer: A is false, R is false. - Assertion (A): Lightning conductors are made of metal.
Reason (R): Metal is a good conductor and can safely transfer charge to the ground.
Answer: Both A and R are true, and R explains A. - Assertion (A): A charged object loses its charge when touched by a conductor.
Reason (R): The charge flows to the earth through the conductor.
Answer: Both A and R are true, and R is the correct explanation of A.
High Order Thinking Skill (HOTS) Questions
- Explain why a charged balloon sticks to a wall after rubbing it on your hair.
Answer: When you rub the balloon on your hair, it gains negative charges. When brought near the wall, it induces positive charges on the surface of the wall. Opposite charges attract, so the balloon sticks to the wall. - Why is it safer to stay inside a car during a thunderstorm?
Answer: The metal body of the car acts as a Faraday cage and directs the lightning current around the passengers, protecting them from electric shock. - How does earthing prevent electric shocks?
Answer: Earthing provides a path for the electric charge to flow safely to the ground, preventing accumulation of charge and electric shocks. - What would happen if the lower end of a lightning conductor is not properly connected to the earth?
Answer: The charge from lightning will not be safely conducted to the ground, increasing the risk of damage or fire. - If two objects are rubbed together and one gains electrons, what happens to the other? Justify your answer.
Answer: The other loses electrons and becomes positively charged. Charges are conserved and always produced in equal and opposite pairs.
Long Questions (50-60 words)
- Explain how charging by friction occurs. Give an example.
Answer: Charging by friction happens when two objects are rubbed together, causing electrons to transfer from one object to the other. This leaves one object negatively charged and the other positively charged. For example, rubbing a plastic comb on wool transfers electrons to the comb, charging it negatively. - Describe the working and importance of a lightning conductor.
Answer: A lightning conductor is a metal rod installed on tall buildings. It provides a low resistance path for lightning to safely flow into the ground, preventing damage or fire. Its lower end must be well connected to the earth to effectively discharge the lightning current. - How does a gold leaf electroscope detect electric charge?
Answer: When a charged object is brought near the metal cap of the electroscope, charge is transferred to the leaves. The leaves, having like charges, repel each other and spread apart. The amount of leaf separation indicates the presence and magnitude of the charge. - Explain the difference between charging by conduction and charging by induction.
Answer: Charging by conduction requires direct contact between a charged and an uncharged object, transferring charge. Charging by induction does not require contact; a charged object induces opposite charges in a nearby neutral object by rearranging its charges. - What precautions should one take during a lightning storm?
Answer: Avoid open fields, tall trees, and metal objects. Stay indoors or inside a vehicle. If caught outside, crouch low with feet close. Avoid using electrical appliances and landline phones to prevent electric shocks.
Additional Questions and Answers – 02
Fill in the Blanks Questions and Answers
- Question: Electricity powers devices like fans, refrigerators, and ______ in our daily life.
Answer: Electricity powers devices like fans, refrigerators, and computers in our daily life. - Question: In the sixteenth century, it was discovered that ______ acquires the property of attracting light objects when rubbed against flannel.
Answer: In the sixteenth century, it was discovered that amber acquires the property of attracting light objects when rubbed against flannel. - Question: An object is said to be electrically ______ if it attracts light objects.
Answer: An object is said to be electrically charged if it attracts light objects. - Question: Metallic objects are typically ______ and do not get charged up on rubbing.
Answer: Metallic objects are typically conductors and do not get charged up on rubbing. - Question: Non-metallic objects like plastic combs are ______ and get charged up on rubbing.
Answer: Non-metallic objects like plastic combs are insulators and get charged up on rubbing. - Question: There are two kinds of charges in nature: positive and ______ charges.
Answer: There are two kinds of charges in nature: positive and negative - Question: Like charges ______ each other, while unlike charges attract.
Answer: Like charges repel each other, while unlike charges attract. - Question: A glass rod, when rubbed against silk, acquires a ______ charge.
Answer: A glass rod, when rubbed against silk, acquires a positive - Question: An ebonite rod, when rubbed against flannel, acquires a ______ charge.
Answer: An ebonite rod, when rubbed against flannel, acquires a negative - Question: Charges are always produced in ______ when two objects are rubbed together.
Answer: Charges are always produced in pairs when two objects are rubbed together. - Question: The process of transferring charge to the earth is called ______.
Answer: The process of transferring charge to the earth is called earthing. - Question: Charging by ______ involves direct physical contact with a charged object.
Answer: Charging by conduction involves direct physical contact with a charged object. - Question: Charging by ______ does not involve direct contact with a charged object.
Answer: Charging by induction does not involve direct contact with a charged object. - Question: Lightning is a sudden electric ______ between clouds or between a cloud and the earth.
Answer: Lightning is a sudden electric discharge between clouds or between a cloud and the earth. - Question: A ______ conductor is a device used to protect tall buildings from lightning.
Answer: A lightning conductor is a device used to protect tall buildings from lightning. - Question: During lightning, it is safer to stay inside a ______ with windows and doors shut.
Answer: During lightning, it is safer to stay inside a car with windows and doors shut. - Question: Lightning converts ______ into its oxide, which helps plants get nitrogenous compounds.
Answer: Lightning converts nitrogen into its oxide, which helps plants get nitrogenous compounds. - Question: A gold leaf ______ is a device used to detect charge on a body.
Answer: A gold leaf electroscope is a device used to detect charge on a body. - Question: In clouds, heavier droplets tend to acquire a ______ charge.
Answer: In clouds, heavier droplets tend to acquire a negative - Question: Lightning can result in the formation of ______ from oxygen, which protects us from UV radiation.
Answer: Lightning can result in the formation of ozone from oxygen, which protects us from UV radiation.
Multiple Choice Questions and Answers
- Question: What role does electricity play in daily life?
a) Powers devices like fans and refrigerators
b) Produces food
c) Cleans water
d) Grows plants
Answer: a) Powers devices like fans and refrigerators - Question: What was discovered about amber in the sixteenth century?
a) It conducts electricity
b) It attracts light objects when rubbed
c) It repels light objects
d) It produces heat
Answer: b) It attracts light objects when rubbed - Question: What is an electrically charged object?
a) An object that repels heavy objects
b) An object that attracts light objects
c) An object that conducts heat
d) An object that produces sound
Answer: b) An object that attracts light objects - Question: Which type of material does not get charged up on rubbing?
a) Plastic
b) Metal
c) Glass
d) Ebonite
Answer: b) Metal - Question: What are non-metallic materials that get charged up on rubbing called?
a) Conductors
b) Insulators
c) Semiconductors
d) Magnets
Answer: b) Insulators - Question: How many kinds of charges exist in nature?
a) One
b) Two
c) Three
d) Four
Answer: b) Two - Question: What happens when like charges interact?
a) They attract each other
b) They repel each other
c) They neutralize each other
d) They produce heat
Answer: b) They repel each other - Question: What charge does a glass rod acquire when rubbed against silk?
a) Negative
b) Positive
c) Neutral
d) No charge
Answer: b) Positive - Question: What charge does an ebonite rod acquire when rubbed against flannel?
a) Positive
b) Negative
c) Neutral
d) No charge
Answer: b) Negative - Question: How are charges produced when two objects are rubbed together?
a) In singles
b) In pairs
c) In groups
d) Not produced
Answer: b) In pairs - Question: What is earthing?
a) Charging an object
b) Transferring charge to the earth
c) Producing lightning
d) Attracting light objects
Answer: b) Transferring charge to the earth - Question: Which method involves charging an object by direct contact?
a) Charging by rubbing
b) Charging by induction
c) Charging by conduction
d) Charging by earthing
Answer: c) Charging by conduction - Question: What does charging by induction involve?
a) Direct contact with a charged object
b) Rubbing two objects together
c) No direct contact with a charged object
d) Heating an object
Answer: c) No direct contact with a charged object - Question: What causes lightning?
a) Electric discharge between clouds or earth
b) Heat from the sun
c) Wind movement
d) Magnetic fields
Answer: a) Electric discharge between clouds or earth - Question: What is the purpose of a lightning conductor?
a) To produce lightning
b) To protect buildings from lightning
c) To charge objects
d) To repel charges
Answer: b) To protect buildings from lightning - Question: Where is it safer to stay during lightning?
a) Under a tree
b) In an open field
c) Inside a car with windows shut
d) Near a tall building
Answer: c) Inside a car with windows shut - Question: What does lightning produce that helps plants?
a) Oxygen
b) Nitrogen oxides
c) Carbon dioxide
d) Sulfur
Answer: b) Nitrogen oxides - Question: What device detects charge on a body?
a) Thermometer
b) Gold leaf electroscope
c) Barometer
d) Magnet
Answer: b) Gold leaf electroscope - Question: In clouds, what charge do heavier droplets typically acquire?
a) Positive
b) Negative
c) Neutral
d) No charge
Answer: b) Negative - Question: What does lightning produce that shields us from UV radiation?
a) Nitrogen
b) Ozone
c) Carbon dioxide
d) Water vapor
Answer: b) Ozone
True/False Questions and Answers
- Question: Electricity powers devices like fans and computers in daily life.
Answer: True - Question: Amber repels light objects when rubbed against flannel.
Answer: False (It attracts light objects.) - Question: An electrically charged object attracts light objects.
Answer: True - Question: Metallic objects get charged up on rubbing.
Answer: False (They are conductors and do not get charged up.) - Question: Non-metallic objects like plastic are insulators.
Answer: True - Question: There are two kinds of charges: positive and negative.
Answer: True - Question: Unlike charges repel each other.
Answer: False (Unlike charges attract each other.) - Question: A glass rod acquires a negative charge when rubbed against silk.
Answer: False (It acquires a positive charge.) - Question: An ebonite rod acquires a negative charge when rubbed against flannel.
Answer: True - Question: Charges are produced in pairs when objects are rubbed together.
Answer: True - Question: Earthing causes a charged object to gain more charge.
Answer: False (It causes the object to lose its charge.) - Question: Charging by conduction involves direct contact with a charged object.
Answer: True - Question: Charging by induction involves rubbing two objects together.
Answer: False (It involves no direct contact.) - Question: Lightning is caused by electric discharge between clouds or the earth.
Answer: True - Question: A lightning conductor increases the chance of lightning strikes.
Answer: False (It reduces the chance and provides a safe path for charges.) - Question: It is safe to stay under a tree during lightning.
Answer: False (It is dangerous.) - Question: Lightning helps plants by producing nitrogen oxides.
Answer: True - Question: A gold leaf electroscope is used to detect charge on a body.
Answer: True - Question: In clouds, lighter droplets tend to acquire a negative charge.
Answer: False (They acquire a positive charge.) - Question: Lightning produces ozone, which protects us from UV radiation.
Answer: True
Short Questions and Answers
- Question: What role does electricity play in daily life?
Answer: Powers devices like fans, refrigerators, and computers. - Question: What was discovered about amber in the sixteenth century?
Answer: It attracts light objects when rubbed against flannel. - Question: What is an electrically charged object?
Answer: An object that attracts light objects. - Question: What are metallic objects typically called in terms of electrical property?
Answer: Conductors. - Question: What are non-metallic objects that get charged up called?
Answer: Insulators. - Question: How many kinds of charges exist in nature?
Answer: Two: positive and negative. - Question: What happens when like charges interact?
Answer: They repel each other. - Question: What charge does a glass rod acquire when rubbed against silk?
Answer: Positive charge. - Question: What charge does an ebonite rod acquire when rubbed against flannel?
Answer: Negative charge. - Question: How are charges produced when two objects are rubbed together?
Answer: In pairs. - Question: What is earthing?
Answer: Transferring charge to the earth. - Question: What does charging by conduction involve?
Answer: Direct contact with a charged object. - Question: What does charging by induction involve?
Answer: No direct contact with a charged object. - Question: What causes lightning?
Answer: Electric discharge between clouds or the earth. - Question: What is the purpose of a lightning conductor?
Answer: To protect buildings from lightning. - Question: Where is it safer to stay during lightning?
Answer: Inside a car with windows shut. - Question: What does lightning produce that helps plants?
Answer: Nitrogen oxides. - Question: What device detects charge on a body?
Answer: Gold leaf electroscope. - Question: What charge do heavier droplets in clouds typically acquire?
Answer: Negative charge. - Question: What does lightning produce that shields us from UV radiation?
Answer: Ozone.
Competency-Based Questions and Answers (Reasoning and Assertion)
- Question: Assertion (A): Metallic objects do not get charged up on rubbing.
Reason (R): They are conductors and allow charges to flow through them easily.
Answer: Both A and R are true, and R is the correct explanation of A. Metallic objects, as conductors, allow charges to flow through them, as stated, preventing charge buildup on their surface during rubbing, unlike insulators, which retain charges, explaining why metals do not get charged up. - Question: Assertion (A): Like charges repel each other.
Reason (R): Unlike charges attract each other.
Answer: A is true, but R is not the correct explanation of A. Like charges repel, as observed with two charged ebonite rods, as noted, but the attraction of unlike charges is a separate phenomenon, not the reason for repulsion, which is due to the nature of electric forces between similar charges. - Question: Assertion (A): Charges are produced in pairs when objects are rubbed together.
Reason (R): One object gains a positive charge, and the other gains a negative charge.
Answer: Both A and R are true, and R is the correct explanation of A. When objects like an ebonite rod and flannel are rubbed, as described, one gains a negative charge and the other a positive charge, ensuring charges are produced in equal and opposite pairs, maintaining overall charge neutrality. - Question: Assertion (A): Earthing removes charge from an object.
Reason (R): The earth acts as a sink for electric charges.
Answer: Both A and R are true, and R is the correct explanation of A. Earthing transfers excess charge to the earth, as stated, which acts as a sink by absorbing or neutralizing the charge, making the object uncharged, a process crucial for safety in electrical appliances to prevent shocks. - Question: Assertion (A): Charging by induction does not involve direct contact.
Reason (R): It separates charges in an uncharged object using a charged object nearby.
Answer: Both A and R are true, and R is the correct explanation of A. Charging by induction, as described, uses a nearby charged object to separate charges in an uncharged object without contact, then earths one end to retain the opposite charge, enabling charging without physical interaction. - Question: Assertion (A): Lightning is caused by electric discharge.
Reason (R): Charges build up in clouds, and air breaks down as an insulator.
Answer: Both A and R are true, and R is the correct explanation of A. Lightning occurs when charges build up in clouds, as noted, and the air, normally an insulator, breaks down, allowing a sudden discharge of charges, resulting in the flash and heat we observe as lightning and thunder. - Question: Assertion (A): A lightning conductor protects buildings from lightning.
Reason (R): It provides a safe path for charges to flow into the earth.
Answer: Both A and R are true, and R is the correct explanation of A. A lightning conductor, as stated, has a metal strip that guides lightning charges safely into the earth, preventing damage to the building by avoiding charge flow through the structure, ensuring safety during lightning strikes. - Question: Assertion (A): It is unsafe to stay under a tree during lightning.
Reason (R): Lightning can strike tall objects like trees, causing damage.
Answer: Both A and R are true, and R is the correct explanation of A. Lightning often strikes tall objects like trees, as noted, due to their height, conducting charges to the ground, which can cause burning or injury, making it unsafe to stay under trees during lightning storms. - Question: Assertion (A): Lightning helps plants grow.
Reason (R): It converts nitrogen into oxides that plants can use.
Answer: Both A and R are true, and R is the correct explanation of A. Lightning converts nitrogen into oxides, as described, which dissolve in rainwater, providing plants with nitrogenous compounds essential for growth, demonstrating a natural benefit of lightning in supporting plant nutrition and agricultural ecosystems. - Question: Assertion (A): A gold leaf electroscope detects charge on a body.
Reason (R): Charges cause the gold leaves to diverge.
Answer: Both A and R are true, and R is the correct explanation of A. A gold leaf electroscope, as stated, detects charge when a charged object causes the gold leaves to diverge due to repulsion of like charges, with the degree of divergence indicating the amount of charge present on the body.
High Order Thinking Skills (HOTS) Questions and Answers
- Question: Why might metals not get charged up on rubbing, and what does this suggest about the role of material properties in charge behaviour?
Answer: Metals, being conductors, allow charges to flow through them easily, as noted, dissipating any charge buildup during rubbing, unlike insulators that retain charges. This suggests material properties like conductivity determine charge behaviour—conductors facilitate charge movement, while insulators trap charges, highlighting how atomic structure influences electrical interactions in different materials. - Question: How does the production of charges in pairs ensure charge conservation, and what does this reveal about fundamental laws of physics?
Answer: When objects are rubbed, one gains a positive charge and the other an equal negative charge, as described, ensuring no net charge is created or lost, conserving total charge. This reveals the law of charge conservation in physics—charge cannot be created or destroyed, only transferred, maintaining balance in all electrical interactions. - Question: Why might charging by induction be preferred for certain applications, and what does this indicate about the precision of charging methods?
Answer: Charging by induction, as stated, allows charging without contact, avoiding charge loss or damage to delicate objects, ideal for sensitive electronics. This indicates charging methods can be precise—induction offers controlled charge separation and transfer, showing how techniques are tailored to specific needs, ensuring safety and efficiency in practical applications. - Question: How does a lightning conductor’s design minimize damage, and what does this suggest about the role of engineering in safety?
Answer: A lightning conductor’s spike reduces charge buildup, and its metal strip provides a safe path for charges into the earth, as noted, preventing structural damage. This suggests engineering plays a key role in safety—designed solutions like lightning conductors mitigate natural hazards, protecting lives and property through strategic charge management. - Question: Why might lightning produce both nitrogen oxides and ozone, and what does this reveal about its environmental impact?
Answer: Lightning’s high energy converts nitrogen into oxides for plants and oxygen into ozone, as described, which shields UV radiation. This reveals lightning’s dual environmental impact—supporting plant growth through nutrient supply while protecting life via ozone formation, highlighting its role in maintaining ecological balance and atmospheric chemistry in nature. - Question: How does the behaviour of charges in clouds lead to lightning, and what does this indicate about the role of insulators in electrical phenomena?
Answer: In clouds, positive and negative charges separate, and air, an insulator, breaks down under high charge buildup, causing discharge as lightning, as noted. This indicates insulators like air play a critical role in electrical phenomena—normally preventing charge flow, their breakdown under stress enables dramatic events like lightning, showing their dynamic behaviour. - Question: Why might it be safer to use a cordless phone during lightning, and what does this suggest about the conductivity of materials in safety protocols?
Answer: Cordless phones, unlike corded ones, aren’t connected to exterior lines that lightning can strike, as stated, reducing shock risk. This suggests material conductivity informs safety protocols—avoiding conductive paths like wired connections during lightning minimizes danger, highlighting how understanding electrical properties of materials enhances safety measures in hazardous situations. - Question: How does earthing prevent electric shocks in appliances, and what does this reveal about the practical applications of charge management?
Answer: Earthing transfers excess charge from appliance bodies to the earth, as described, keeping them uncharged and preventing shocks to users. This reveals charge management’s practical applications—earthing ensures safety in electrical systems, showing how controlling charge flow protects users, a fundamental principle in designing safe electrical devices for everyday use. - Question: Why might a gold leaf electroscope be effective in detecting charges, and what does this indicate about the sensitivity of charge detection methods?
Answer: A gold leaf electroscope detects charges as like charges on the leaves cause divergence, as stated, with the degree indicating charge amount, due to gold’s conductivity and lightness. This indicates charge detection methods are highly sensitive—small charges cause visible effects, enabling precise measurement, crucial for experiments and safety in electrical studies. - Question: How does the attraction and repulsion of charges demonstrate the nature of electric forces, and what does this suggest about the fundamental interactions in physics?
Answer: Like charges repel and unlike charges attract, as observed in ebonite and glass rod experiments, showing electric forces depend on charge type, as noted. This suggests fundamental interactions in physics—like charges create repulsive forces, while opposites attract—govern all electrical phenomena, forming the basis for understanding electricity and its applications in nature.
Long Questions and Answers (50-60 Words)
- Question: Describe how electricity is used in daily life.
Answer: Electricity powers devices like fans, refrigerators, and computers, as stated, lighting homes with bulbs, cooling food, and enabling entertainment via TVs. It runs metro trains for commuting, supports farming with electric pumps, and drives factories producing clothes and food, highlighting its vital role in modern life, making daily tasks efficient and comfortable for everyone. - Question: Explain the discovery of electric charge using amber.
Answer: In the sixteenth century, it was found that amber, when rubbed against flannel, attracts light objects like paper, as described, acquiring an electric charge. This property, absent without rubbing, led to the term “electric” from the Greek “elektron” for amber, marking the early understanding of charge generation through friction in the study of electricity. - Question: Discuss the difference between conductors and insulators.
Answer: Conductors, like metals, allow electric charges to flow easily and don’t get charged up on rubbing, as noted, while insulators, like plastic, resist charge flow, getting charged up. Conductors facilitate electricity in wires, while insulators prevent unwanted flow in cables, showing their distinct roles in managing charge movement in electrical applications. - Question: Describe the behavior of like and unlike charges.
Answer: Like charges repel each other, as seen with two charged ebonite rods moving apart, while unlike charges attract, as a charged ebonite rod attracts a charged glass rod, as stated. This behavior, identified as positive and negative charges, demonstrates the fundamental rule of electric forces, governing interactions in all charged objects in nature. - Question: Explain the process of charging by conduction.
Answer: Charging by conduction involves direct contact with a charged object, as described, where an uncharged object, like a pith ball, touches a charged glass rod, sharing its charge. The uncharged object gains a similar charge, repelling afterward, with the charge amount depending on the objects’ sizes and materials, illustrating charge transfer through physical contact. - Question: Discuss the process of charging by induction.
Answer: Charging by induction separates charges in an uncharged object using a nearby charged object without contact, as stated. The uncharged object is earthed, losing opposite charges to the earth, then isolated, retaining a charge opposite to the initial object. This method, avoiding direct contact, charges objects safely, often used in sensitive applications. - Question: Describe how lightning occurs in nature.
Answer: Lightning occurs when charges build up in clouds, with heavier droplets gaining negative charges and lighter ones positive, as noted. Air, an insulator, breaks down under high charge, causing a sudden electric discharge between clouds or the earth. This discharge heats the air, producing a flash seen as lightning, accompanied by thunder from rapid air expansion. - Question: Explain the role of a lightning conductor in protecting buildings.
Answer: A lightning conductor, a metal strip with a spike, reduces charge buildup on clouds and provides a safe path for lightning charges to flow into the earth, as described. Installed on tall buildings, it prevents damage by diverting charges away from the structure, ensuring safety during lightning strikes by effective charge management. - Question: Discuss safety precautions during lightning.
Answer: During lightning, stay inside a car or building with windows shut, avoiding open areas and trees, as stated. Inside, avoid water contact, electric equipment like TVs, and corded phones, using cordless ones instead. These precautions minimize the risk of lightning strikes, ensuring safety by reducing exposure to conductive paths during storms. - Question: Describe the advantages of lightning in nature.
Answer: Lightning converts nitrogen into oxides, aiding plant growth, and forms ozone from oxygen, shielding UV radiation, as noted. It also balances earth’s electric charges by transferring huge amounts during strikes. These benefits highlight lightning’s role in supporting ecosystems, enhancing plant nutrition, and protecting life through atmospheric chemistry, despite its destructive potential.