One Mark Questions Answers

MAGNETISM AND ELECTROMAGNETISM

TEXT BOOK EXERCISES

I. Choose the correct answer :

1. Which of the following converts electrical energy into mechanical energy?

(a) Motor

(b) Battery

(c) Generator

(d) Switch

[Answer: (a) Motor]

2. Transformer works on _――― .

(a) AC only

(b) DC only

(c) Both AC and DC

[Answer: (a) AC only]

3. The part of the AC generator that passes the current from the armature coil to the external circuit is

(a) field magnet

(b) split rings

(c) slip rings

(d) brushes

[Answer: (d) brushes]

4. The unit of magnetic flux density is

(a) Weber

(b) weber/metre

(c) weber/metre²

(d) weber.metre²

[Answer: (c) weber/metre²]

II. Fill in the blanks :

1. The SI Unit of magnetic field induction is Tesla _.

2. Devices which is used to convert high alternating current to low alternating current is transformers

3. An electric motor converts electrical energy into mechanical energy .

4. A device for producing electric current is generator .

III. Match the following :

1. Magnetic material - a) Oersted

2. Non-magnetic material - b) Iron

3. Current and magnetism - c) Induction

4. Electromagnetic induction - d) Wood

5. Electric generator - e) Faraday

Answer: 1-b, 2-d, 3-a, 4-e, 5-c

1. Magnetic material - Iron

2. Non-magnetic material - Wood

3. Current and magnetism - Oersted

4. Electromagnetic induction - Faraday

5. Electric generator - Induction

IV. State whether true or false. If false, correct the statement:

1. A generator converts mechanical energy into electrical energy.

Answer: True.

2. Magnetic field lines always repel each other and do not intersect.

Answer: True.

3. Fleming’s Left hand rule is also known as Dynamo rule.

Answer: False.

Correct statement: Fleming's Left hand rule is also known as motor rule.

4. The speed of rotation of an electric motor can be increased by decreasing the area of the coil.

Answer: False.

Correct statement: The speed of rotation of an electric motor can be increased by increasing the area of the coil.

5. A transformer can step up direct current.

Answer: False.

Correct statement: A transformer can step up alternating current (AC).

6. In a step down transformer the number of turns in primary coil is greater than that of the number of turns in the secondary coil.

Answer: True.