Magnetism And Matter — Physics STD 12 Science — Question

The power rating of an electric motor which draws a current  of 3.75 amperes when operated at 200 V is about

(a) 1 H.P.

(b) 500 W

(c) 54 W

(d) 750 H.P.

If an electron and a positron annihiliate, then the energy released is

(a) 3.2

(b) 1.6

(c) 4.8

(d) 6.4

In Young's experiment, the distance between the slits is reduced to half and the distance between the slit and screen is doubled, then the fringe width

(a) Will not change	(b) Will become half
(c) Will be doubled	(d) Will become four times

Resistances of 6 ohm each are connected in the manner shown in adjoining figure. With the current 0.5 ampere as shown in figure, the potential difference  is

(a) 3.6 V

(b) 6.0 V

(c) 3.0 V

(d) 7.2 V

When the length of the tube of a microscope is increased, the magnifying power will be :

The equivalent resistance between P and Q in the given figure, is

(a) 50 W

(b) 40 W

(c) 30 W

(d) 20 W

A transformer is employed to

(a) Obtain a suitable dc voltage	(b) Convert dc into ac
(c) Obtain a suitable ac voltage	(d) Convert ac into dc

A wire carrying current i is shaped as shown. Section AB is a quarter circle of radius r.  The magnetic field is directed

(a) At an angle π/4  to the plane of the paper

(b) Perpendicular to the plane of the paper and directed in to the paper

(c) Along the bisector of the angle ACB  towards AB

(d) Along the bisector of the angle ACB away from AB

The voltage gain of a triode depends upon

(a) Filament voltage

(b) Plate voltage

(c) Plate resistance

(d) Plate current