Current Electricity — Physics STD 12 Science — Question

An intrinsic semiconductor is:

The refractive index of water is 4 / 3 and that of glass is 5/3.  What will be the critical angle for the ray of light entering water from the glass  

(a)

(b)

(c)

(d)

A block is placed on a rough floor and a horizontal force F is applied on it. The force of friction f by the floor on the block is measured for different values of F and a graph is plotted between them.

1. The graph is a straight line of slope 45°.
2. The graph is a straight line parallel to the F-axis.
3. The graph is a straight line of slope 45° for small F and a straight line parallel to the F-axis for large F.
4. There is a small kink on the graph.

A solid conducting sphere of radius a has a net positive charge 2Q. A conducting spherical shell of inner radius  b and outer radius c is concentric with the solid sphere and has a net charge – Q. The surface charge density on the inner and outer surfaces of the spherical shell will be

(a)

(b)

(c) 0,

(d) None of the above

Huygens' wave theory is used:

 For television broadcasting the frequency employed is normally:

For copper-iron (Cu-Fe) couple, the thermo e.m.f. (temperature of cold junction = 0℃) is given by E = (14θ – 0.02)μV. The neutral temperature will be

(a) 350 ℃

(b) 350 K

(c) 560℃

(d) 560 K

When the current through a solenoid increases at a constant rate, the induced current

(a) Is constant and is in the direction of the inducing current

(b) Is a constant and is opposite to the direction of the inducing current

(c) Increases with time and is in the direction of the inducing current

(d) Increases with time and opposite to the direction of the inducing current

In Young's experiment, one slit is covered with a blue filter and the other (slit) with a yellow filter. Then the interference pattern

(a) Will be blue

(b) Will be yellow

(c) Will be green

(d) Will not be formed