✅ True or False (10 Questions)

(CBSE Class 8 Standard | Good Quality)

1. When electric current flows through a wire, it produces a magnetic field around it.
   True hecu104

2. The magnetic effect of electric current was discovered by Hans Christian Oersted.
   True hecu104

3. A compass needle does not deflect near a current-carrying wire.
   False
   (It deflects due to magnetic field.) hecu104

4. An electromagnet works only when electric current flows through it.
   True hecu104

5. An electromagnet remains magnetic even after the current is switched off.
   False
   (It loses magnetism when current stops.) hecu104

6. The strength of an electromagnet can be increased by increasing the number of turns of the coil.
   True hecu104

7. Nichrome wire is used in heating appliances because it has high resistance.
   True hecu104

8. Heating effect of electric current is always harmful and has no useful applications.
   False
   (It is useful in heaters, irons, stoves, etc.) hecu104

9. A dry cell uses a thick paste electrolyte instead of liquid electrolyte.
   True hecu104

10. Used batteries should be thrown in regular garbage as they are completely harmless.
    False
    (They must be recycled properly.)

✅ Fill in the Blanks (10 Questions)

(CBSE Class 8 Standard | Good Quality)

1. A current-carrying wire produces a __________ field around it.
   Answer: magnetic hecu104

2. The magnetic effect of electric current was discovered by __________.
   Answer: Oersted hecu104

3. A device that shows direction using Earth’s magnetism is called a __________.
   Answer: compass hecu104

4. A temporary magnet made using electric current is called an __________.
   Answer: electromagnet hecu104

5. The strength of an electromagnet increases with increase in the number of __________ of the coil.
   Answer: turns hecu104

6. Electromagnets are widely used in __________ cranes to lift scrap iron.
   Answer: lifting hecu104

7. The heating effect of electric current is due to the __________ of the wire.
   Answer: resistance hecu104

8. __________ wire is used in electric heaters because it has high resistance.
   Answer: nichrome hecu104

9. A dry cell contains electrolyte in the form of a thick __________.
   Answer: paste hecu104

10. Used batteries should be disposed of safely by __________ them.
    Answer: recycling

✅ Multiple Choice Questions (15 MCQs)

Chapter 4: Electricity – Magnetic and Heating Effects

(CBSE Class 8 Standard | Good Quality)

1. A magnetic field is produced around a wire when:

A. No current flows
B. Electric current flows
C. Wire is broken
D. Wire is insulated
✅ Answer: B hecu104

2. The magnetic effect of current was discovered by:

A. Newton
B. Edison
C. Oersted
D. Faraday
✅ Answer: C hecu104

3. A compass needle deflects near a current-carrying wire because of:

A. Heat
B. Light
C. Magnetic field
D. Gravity
✅ Answer: C hecu104

4. An electromagnet is a:

A. Permanent magnet
B. Temporary magnet
C. Natural magnet
D. Stone magnet
✅ Answer: B hecu104

5. The strength of an electromagnet can be increased by:

A. Reducing current
B. Reducing turns
C. Increasing turns of coil
D. Using plastic core
✅ Answer: C hecu104

6. Which material is generally used as core in an electromagnet?

A. Wood
B. Plastic
C. Soft iron
D. Glass
✅ Answer: C hecu104

7. Electromagnets are used in cranes to lift:

A. Paper
B. Scrap iron
C. Water
D. Sand
✅ Answer: B hecu104

8. The heating effect of electric current is due to:

A. Reflection
B. Resistance
C. Magnetism
D. Gravity
✅ Answer: B hecu104

9. Nichrome wire is used in heaters because it has:

A. Low resistance
B. High resistance
C. No resistance
D. Magnetic property
✅ Answer: B hecu104

10. Electric iron works on the principle of:

A. Magnetic effect
B. Heating effect
C. Chemical effect
D. Sound effect
✅ Answer: B hecu104

11. A dry cell contains electrolyte in the form of:

A. Gas
B. Thick paste
C. Solid metal
D. Ice
✅ Answer: B hecu104

12. The positive terminal of a dry cell is usually made of:

A. Carbon rod
B. Zinc container
C. Copper wire
D. Plastic cover
✅ Answer: A hecu104

13. Rechargeable batteries are used in:

A. Toys only
B. Cars and mobiles
C. Rocks
D. Candles
✅ Answer: B hecu104

14. Used batteries should be:

A. Thrown in dustbin
B. Burnt
C. Recycled safely
D. Stored in water
✅ Answer: C hecu104

15. Which of the following is NOT an application of heating effect?

A. Electric heater
B. Electric bulb
C. Compass needle
D. Electric iron
✅ Answer: C

✅ Assertion–Reason Questions (10)

(CBSE Class 8 Standard | Good Quality)

Directions: Choose the correct option:

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true

1.

Assertion (A): A current-carrying wire produces a magnetic field around it.
Reason (R): Electric current creates magnetic effect.
✅ Answer: A hecu104

2.

Assertion (A): A compass needle deflects near a current-carrying wire.
Reason (R): The wire behaves like a magnet when current flows through it.
✅ Answer: A hecu104

3.

Assertion (A): Electromagnets are temporary magnets.
Reason (R): They lose magnetism when current is switched off.
✅ Answer: A hecu104

4.

Assertion (A): The strength of an electromagnet increases with more turns of coil.
Reason (R): More turns produce stronger magnetic field.
✅ Answer: A hecu104

5.

Assertion (A): Soft iron is used as core of electromagnets.
Reason (R): Soft iron gets magnetised easily and loses magnetism quickly.
✅ Answer: A hecu104

6.

Assertion (A): Nichrome is used in heating appliances.
Reason (R): Nichrome has high resistance and produces heat when current flows.
✅ Answer: A hecu104

7.

Assertion (A): Heating effect of current is useful in electric irons and heaters.
Reason (R): Electric current produces heat due to resistance in wire.
✅ Answer: A hecu104

8.

Assertion (A): A dry cell is more convenient than a voltaic cell.
Reason (R): A dry cell contains electrolyte in paste form and does not spill.
✅ Answer: A hecu104

9.

Assertion (A): Used batteries should not be thrown in garbage.
Reason (R): Batteries contain harmful chemicals that pollute the environment.
✅ Answer: A hecu104

10.

Assertion (A): Electromagnets are used in cranes.
Reason (R): They can be switched on and off to lift and drop scrap iron.
✅ Answer: A

✅ Very Short Answer Questions (10 Questions)

(2 Marks Each | CBSE Class 8 Standard | Good Quality)

1. What is the magnetic effect of electric current?

Answer:
The magnetic effect of electric current means that a current-carrying wire produces a magnetic field around it. hecu104

2. Who discovered the magnetic effect of current?

Answer:
Hans Christian Oersted discovered the magnetic effect of electric current. hecu104

3. What is an electromagnet?

Answer:
An electromagnet is a temporary magnet produced by passing electric current through a coil of wire wound around a soft iron core. hecu104

4. Why is soft iron used in electromagnets?

Answer:
Soft iron is used because it gets magnetised easily and loses magnetism quickly when current is switched off. hecu104

5. Mention one use of electromagnets.

Answer:
Electromagnets are used in cranes to lift heavy scrap iron. hecu104

6. What is the heating effect of electric current?

Answer:
The heating effect of electric current is the production of heat in a wire when electric current passes through it due to resistance. hecu104

7. Why is nichrome wire used in electric heaters?

Answer:
Nichrome wire is used because it has high resistance and produces a large amount of heat when current flows through it. hecu104

8. What is a dry cell?

Answer:
A dry cell is an electric cell in which electrolyte is present in the form of a thick paste, making it portable and leak-proof. hecu104

9. Give one example of an electric heating appliance.

Answer:
Electric iron, electric heater, and toaster are examples of heating appliances. hecu104

10. Why should used batteries be recycled?

Answer:
Used batteries contain harmful chemicals, so they should be recycled to prevent environmental pollution.

✅ Short Answer Questions (10 Questions)

(3 Marks Each | CBSE Class 8 Standard | Good Quality)

1. Describe Oersted’s experiment to show magnetic effect of current.

Answer:
Oersted placed a compass needle near a wire carrying electric current. The compass needle deflected, showing that a current-carrying wire produces a magnetic field around it. This proved the magnetic effect of electric current. hecu104

2. Explain how an electromagnet is made.

Answer:
An electromagnet is made by winding a coil of insulated copper wire around a soft iron core. When electric current passes through the coil, the iron core becomes magnetised and acts as a magnet. hecu104

3. How can the strength of an electromagnet be increased?

Answer:
The strength of an electromagnet can be increased by:

• Increasing the number of turns of the coil
• Increasing the current flowing through the coil
• Using a soft iron core hecu104

4. Give two uses of electromagnets.

Answer:
Electromagnets are used in:

• Cranes to lift scrap iron
• Electric bells and relays hecu104

5. What is the heating effect of electric current? Explain with an example.

Answer:
When electric current flows through a wire, heat is produced due to resistance. This is called heating effect of current. Example: Electric iron produces heat to press clothes. hecu104

6. Why is nichrome used in heating appliances?

Answer:
Nichrome is used because it has high resistance, high melting point, and does not oxidise easily. It produces more heat when current passes through it. hecu104

7. Differentiate between voltaic cell and dry cell.

Answer:
A voltaic cell contains liquid electrolyte and may spill, while a dry cell contains electrolyte in paste form, making it portable and safer to use. hecu104

8. What are rechargeable batteries? Mention one use.

Answer:
Rechargeable batteries are batteries that can be used again after charging. They are used in mobile phones, laptops, and electric cars. hecu104

9. Why should we not throw used batteries in garbage?

Answer:
Used batteries contain toxic chemicals and heavy metals. Throwing them in garbage can pollute soil and water, so they must be recycled safely. hecu104

10. How does an electromagnet help in lifting scrap iron?

Answer:
Electromagnets in cranes become magnetic when current flows, attracting scrap iron. When current is switched off, magnetism disappears and the scrap iron is released.

✅ Case-Based Questions (4 Cases)

(4 Marks Each | Sub-questions: 1 + 1 + 2 Marks)
CBSE Competency-Based Standard

Case 1: Compass Near a Wire

A student places a compass needle near a wire. When electric current flows through the wire, the compass needle deflects.

Questions:

Q1. (1 Mark) What does the deflection of compass needle show?
Answer: Current produces a magnetic field. hecu104

Q2. (1 Mark) Who discovered this magnetic effect of current?
Answer: Oersted hecu104

Q3. (2 Marks) Why does the compass needle deflect near the wire?
Answer:
Because a current-carrying wire behaves like a magnet and produces a magnetic field that affects the compass needle. hecu104

Case 2: Electromagnet in a Crane

Scrap yards use cranes fitted with electromagnets to lift heavy iron pieces. The magnet can be switched on and off.

Questions:

Q1. (1 Mark) What type of magnet is used in cranes?
Answer: Electromagnet hecu104

Q2. (1 Mark) What happens when current is switched off?
Answer: Magnetism disappears. hecu104

Q3. (2 Marks) Why are electromagnets preferred over permanent magnets in cranes?
Answer:
Because electromagnets can be switched on to lift scrap iron and switched off to release it easily. hecu104

Case 3: Heating Effect in Appliances

Electric heaters and irons use a special wire that becomes hot when current passes through it.

Questions:

Q1. (1 Mark) Name the wire used in heating appliances.
Answer: Nichrome hecu104

Q2. (1 Mark) What effect of current is used here?
Answer: Heating effect hecu104

Q3. (2 Marks) Why does the wire become hot when current flows?
Answer:
Because the wire offers resistance to current and electrical energy is converted into heat energy. hecu104

Case 4: Safe Disposal of Batteries

A student learns that used batteries contain harmful chemicals and should not be thrown in garbage.

Questions:

Q1. (1 Mark) Why are used batteries harmful?
Answer: They contain toxic chemicals. hecu104

Q2. (1 Mark) What should be done with used batteries?
Answer: They should be recycled. hecu104

Q3. (2 Marks) How does recycling batteries help the environment?
Answer:
Recycling prevents harmful chemicals from polluting soil and water and allows reuse of useful materials.

✅ Long Answer Questions (5 Questions)

(5 Marks Each | CBSE Class 8 Standard | High Quality Answers)

1. Explain the magnetic effect of electric current with Oersted’s experiment.

Answer:
The magnetic effect of electric current means that when current flows through a wire, a magnetic field is produced around it.

Oersted’s Experiment:

• Oersted placed a compass needle near a straight wire.
• When current was passed through the wire, the compass needle deflected.
• When current was switched off, the needle returned to its original position.

This proved that a current-carrying wire behaves like a magnet and produces a magnetic field around it. hecu104

2. What is an electromagnet? How is it made and used?

Answer:
An electromagnet is a temporary magnet produced by passing electric current through a coil wound around a soft iron core.

Making an Electromagnet:

• Wrap insulated copper wire around a soft iron nail.
• Connect the wire to a battery.
• When current flows, the nail becomes magnetic.

Uses:

• Cranes to lift scrap iron
• Electric bells and motors

Electromagnets are useful because they can be switched on and off. hecu104

3. Explain the heating effect of electric current and its applications.

Answer:
When electric current flows through a wire, the wire becomes hot due to resistance. This is called the heating effect of current.

Cause:

Electrical energy is converted into heat energy when current passes through a resistor.

Applications:

• Electric iron
• Electric heater
• Electric toaster
• Electric bulb filament

Thus, heating effect is widely used in daily life appliances. hecu104

4. Why is nichrome used in heating appliances?

Answer:
Nichrome is commonly used as a heating element because:

• It has high electrical resistance, producing more heat.
• It has a high melting point, so it does not melt easily.
• It does not oxidise quickly at high temperatures.

Therefore, nichrome is ideal for appliances like heaters, irons, and stoves. hecu104

5. Describe different types of electric cells and the importance of recycling batteries.

Answer:

Types of Cells:

1. Voltaic Cell: Contains liquid electrolyte and may spill.
2. Dry Cell: Contains electrolyte in paste form and is portable.
3. Rechargeable Batteries: Can be charged and reused in mobiles, laptops, etc.

Importance of Recycling:

Used batteries contain harmful chemicals and heavy metals. If thrown in garbage, they pollute soil and water. Recycling helps in safe disposal and reuse of materials.

Thus, batteries should always be recycled properly.