# electric current and magnetism - Category wise Question and Answer Practice Test with Solutions

#### electric current and magnetism PRACTICE TEST [9 - EXERCISES]

Question : 1

An AC generator of 220 V having internal resistance r = 10Ω and external resistance R = 100Ω. What is the power developed in the external circuit?

a) 400 W

b) 441 W

c) 484 W

d) 369 W

V = 200V; r = 10Ω

R' = 10 + 100Ω = 110Ω

I = \$V/R' = 220/100 = 2A\$

P=\$I^2R\$ = 4 × 100 = 400 W

Question : 2

Consider the following statements :

1. Magnetic field produced by current in a straight wire has no poles.
2. The magnetic lines of force produced by a straight current carrying conductor are straight in nature.
3. To produce a strong magnetic field at its centre, we prefer a current carrying wire loop of larger radius.
Which of these statements is/are correct?

a) 1 only

b) 1 and 3

c) 2 only

d) 1, 2 and 3

Magnetic field lines form in concentric circles around a cylindrical current-carrying conductor, such as a length of wire.

The strength of the magnetic field at the centre of a circular coil carrying current is inversely proportional to the radius of the circular coil.

i.e. the field strength reduces as the radius of the coil increases.

Question : 3

Out of the following, diamagnetic substance is

b) iron

c) copper

d) silver

Copper has negative susceptibility

(i.e. χ = –0.96). Hence, it is diamagnetic.

Question : 4

The length of a wire is doubled and the radius is doubled. By what factor does the resistance change?

a) Twice as large

b) Unchanged

c) 4 times as large

d) Half as large

Question : 5 [NDA]

A ray of ligh is incident normally on one of the faces of right angled isosceles prism as shhown above. It undergoes total internal reflection from hypotenuse. Which one of the following is the minimum refractive index of the material of the prism?

a) 1.414

b) 1.0

c) 1.33

d) 1.6

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