Updated By SaraNextGen

On March 11, 2024, 11:35 AM

Question 1:

Which of the following correctly describes the magnetic field near a long straight wire?

(a) The field consists of straight lines perpendicular to the wire

(b) The field consists of straight lines parallel to the wire

(c) The field consists of radial lines originating from the wire

(d) The field consists of concentric circles centred on the wire

Answer:

(d) The magnetic field lines, produced around a straight current-carrying conductor, are concentric circles. Their centres lie on the wire.

Question 2:

The phenomenon of electromagnetic induction is

(a) the process of charging a body

(b) the process of generating magnetic field due to a current passing through a coil

(c) producing induced current in a coil due to relative motion between a magnet and the coil

(d) the process of rotating a coil of an electric motor

Answer:

(c) When a straight coil and a magnet are moved relative to each other, a current is induced in the coil. This phenomenon is known as electromagnetic induction.

Question 3:

The device used for producing electric current is called a

(a) generator

(b) galvanometer

(c) ammeter

(d) motor

Answer:

(a) An electric generator produces electric current. It converts mechanical energy into electricity.

Question 4:

The essential difference between an AC generator and a DC generator is that

(a) AC generator has an electromagnet while a DC generator has permanent magnet.

(b) DC generator will generate a higher voltage.

(c) AC generator will generate a higher voltage.

(d) AC generator has slip rings while the DC generator has a commutator.

Answer:

(d) An AC generator has two rings called slip rings. A DC generator has two half rings called commutator. This is the main difference between both the types of generators.

Question 5:

At the time of short circuit, the current in the circuit

(a) reduces substantially

(b) does not change

(c) increases heavily

(d) vary continuously

Answer:

(c) When two naked wires of an electric circuit touch each other, the amount of current that is flowing in the circuit increases abruptly. This causes short-circuit.

Question 6:

State whether the following statements are true or false.

(a) An electric motor converts mechanical energy into electrical energy.

(b) An electric generator works on the principle of electromagnetic induction.

(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.

(d) A wire with a green insulation is usually the live wire of an electric supply.

Answer:

(a) False

An electric motor converts electrical energy into mechanical energy.

(b) True

A generator is an electric device that generates electricity by rotating a coil in a magnetic field. It works on the principle of electromagnetic induction.

(c) True

A long circular coil is a long solenoid. The magnetic field lines inside the solenoid are parallel lines.

(d) False

Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.

Question 7:

List three sources of magnetic fields.

Answer:

Three sources of magnetic fields are as follows:

(a) Current-carrying conductors

(b) Permanent magnets

(c) Electromagnets