Electromagnets

Q. What is solenoid?

Q. A solenoid 1.5m long and 4.0cm in diameter possesses 10turns/cm .A current of 5A is flowing through it .Then the magnetic induction inside is?

Q. Electromagnets are used in cranes to pick heavy metallic objects.

1. True
2. False

Q.

Why electromagnets are called temporary magnets?

Q.

What is an artificial magnet?

Q.

A magnet attracts iron fillings towards it. Does the magnet do any work?

Q. Which of the following objects make use of an electromagnet?

1. 
2. 
3. 
4. 

Q.

What is the difference between coil and inductor?

Q. Study the statements given below:
(i) Electromagnets can be made more powerful than ordinary bar magnets.
(ii) Soft iron is easy to magnetize and demagnetize.
(iii) The poles of an electromagnet are not affected by the direction of the current.
Which of the above statements are correct?

1. Only (i) and (ii)
2. Only (ii) and (iii)
3. (i), (ii) and (iii)
4. Only (i) and (iii)

Q.

Permanent magnets are made of steel.

1. True
2. False

Q.

Working of an electromagnet is based on ___.

1. Heating effect of electric current

2. Electro-chemical effect of electric current

3. Magnetic effect of electric current

4. Chemical effect of electric current

Q.

An electric bell contains an electromagnet which helps the bell to ring.

1. True

2. False

Q.

An electric bell consists of ___

1. a hammer

2. a metal gong

3. a battery

4. a rotating coil

Q.

Question 9 (c)
Mark ‘T’ if the statement is true and ‘F’ if it is false:
An electromagnet does not attract a piece of iron.

Q. What is neodymium magnets? How it is different from other magnets?

Q.

The direction of the current can be reversed in an electromagnet but not its pole.

1. True
2. False

Q. The incomplete diagram of an electric bell is given in the figure. Complete the diagram and label its different parts.

Q. Which of the following statements is false regarding an electromagnet?

1. It is a permanent magnet
2. It works only in the presence of electricity
3. It can easily be magnetized and demagnetized
4. It is used in fan and radio

Q. The most effective method of magnetisation is ___________.

1. Single touch method
2. Double touch method
3. All the above
4. Electrical method

Q.

An electric bell works on the principle of electromagnetic induction

1. True
2. False

Q. We can change the strength of electromagnets by changing the amount of electricity which is passing through them. Now, answer the following question: The electromagnets are ___________

1. Permanent magnets

2. Temporary magnets

3. Not magnets

4. Always stronger than magnets which occur naturally in nature

Q.

Mention five differences between an electromagnet and permanent magnet. [5 MARKS]

Q. Label the parts of the given electric bell.

1. P - Hammer, Q - Contact screw, R - Gong, S - Electromagnet
2. P - Contact screw, Q - Hammer, R - Electromagnet, S - Gong
3. P - Electromagnet, Q - Gong, R - Contact screw, S - Hammer
4. P - Hammer, Q - Contact screw, R - Electromagnet, S - Gong

Q. Which part of the electric bell vibrates to produce the sound that we listen?

1. 
2. 
3. 
4. 

Q.

Which of the following is true regarding solenoids?

(A) strength of the magnetic field is independent of the material on which the coil is wound.

(B) when the coil is wound around a soft iron core, it behaves like a temporary magnet.

1. Only A

2. Only B

3. Both A and B

4. None of the above

Q.

Two solenoids, ‘P’ and ‘Q’ are taken. The coil in solenoid ‘P’ is wound over a wooden cylindrical core and the coil in solenoid ‘Q’ is wound over a soft iron core. In which solenoid is the magnetic field stronger?

Q. State two common uses of electromagnets.
[2 Marks]

Q.

Negative plate of an uncharged Edison accumulator contains _________.

Q.

____________ is a device which converts electrical energy into mechanical energy.

1. fan

2. cooler

3. heater

4. motor

Q.

How do you make slip rings?