AC generators, power plants, etc., produce alternating current.

A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each

(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution

Ans (c) half revolution
(c) When a rectangular coil of copper is rotated in a magnetic field, the direction of the induced current in the coil changes once in each half revolution. As a result, the direction of current in the coil remains the same.

Two safety measures commonly used in electric circuits and appliances are
→ Electric Fuse: An electric fuse is connected in series it protects the circuit from overloading and prevents it from short circuiting.
→ Proper earthing of all electric circuit in which any leakage of current in an electric appliance is transferred to the ground and people using the appliance do not get the shock.

Current drawn by the electric oven can be obtained by the expression,
P = VI

Where,
Current = I
Power of the oven, P = 2 kW = 2000 W
Voltage supplied, V = 220 V

I = 2000/220 V = 9.09 A
Hence, the current drawn by the electric oven is 9.09 A, which exceeds the safe limit of the circuit. Fuse element of the electric fuse will melt and break the circuit.

The precautions that should be taken to avoid the overloading of domestic circuits are as follows:
→ Too many appliances should not be connected to a single socket.
→ Too many appliances should not be used at the same time.
→ Faulty appliances should not be connected in the circuit.
→ Fuse should be connected in the circuit.

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

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

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

The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter
(d) motor
ANS (a) generator
An electric generator produces electric current. It converts mechanical energy into electricity.