Magnetism and Electromagnetism

Samacheer Book Back Questions And Answers For Science Standard 9 “Magnetism and Electromagnetism“

I. Choose the correct answer:
1. Which of the following converts electrical energy into mechanical energy?
(a) Motor
(b) Battery
(c) Generator
(d) Switch

2. Transformer works on _____.
(a) AC only
(b) DC only
(c) Both AC and DC

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

4. The unit of magnetic flux density is
(a) Weber
(b) weber/metre
(c) weber/metre²
(d) weber.metre²

II. Fill in the blanks:
1. The SI Unit of magnetic field induction is _____.
2. Devices which is used to convert high alternating current to low alternating current is _____.
3. An electric motor converts _____.
4. A device for producing electric current is _____.

Answers:
1. Tesla
2. transformers
3. electrical energy into mechanical energy
4. 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

Answers:
1. B
2. D
3. A
4. E
5. C

IV. State whether true or false. If false, correct the statement:
1. A generator converts mechanical energy into electrical energy.
2. Magnetic field lines always repel each other and do not intersect.
3. Fleming’s Left hand rule is also known as Dynamo rule.
4. The speed of rotation of an electric motor can be increased by decreasing the area of the coil.
5. A transformer can step up direct current.
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.

Answers:
1. True
2. True
3. False (Fleming’s Left hand rule is also known as motor rule)
4. False (The speed of rotation of an electric motor can be increased by increasing the area of the coil)
5. False (A transformer can step up alternating current)
6. True

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