Nucleus — Physics STD 12 Science — Question

The graph shows the variation of magnetic field (B)with distance (r) from a long current carrying wire is-

AB is a potentiometer wire of length 100 cm and its resistance is 10 ohms.  It is connected in series with a resistance R = 40 ohms and a battery of e.m.f. 2 V and negligible internal resistance.  If a source of unknown e.m.f. E is balanced by 40 cm length of the potentiometer wire, the value of E is

(a) 0.8 V

(b) 1.6 V

(c) 0.08 V

(d) 0.16 V

Electron-volt (eV) is the measure of:

A thin oil layer floats on water. A ray of light making an angle of incidence of 40° shines on oil layer. The angle of refraction of light ray in water  is ()

(a) 36 .1°

(b) 44.5°

(c) 26. 8°

(d) 28.9°

There is a small hole near the bottom of an open tank filled with a liquid. The speed of the water ejected does not depend on.

1. Area of the hole.
2. Density of the liquid.
3. Height of the liquid from the hole.
4. Acceleration due to gravity.

A bar magnet of magnetic moment   is placed in a magnetic field of induction . The torque exerted on it is

(a)

(b) -

(c)

(d)

An electron moving with a speed u along the positive x-axis at y = 0 enters a region of uniform magnetic field   which exists to the right of y-axis. The electron exits from the region after some time with the speed v at co-ordinate y, then

(a) v > u, y < 0

(b) v = u, y > 0

(c) v > u, y > 0

(d) v = u, y < 0

The dispersive power of the material of lens of focal length 20 cm is 0.08. The longitudinal chromatic aberration of the lens is

(a) 0.08 cm

(b) 0.08/20 cm

(c) 1.6 cm

(d) 0.16 cm

A 20cm long capillary tube is dipped in water. The water rises up to 8cm. If the entire arrangement is put in a freely falling elevator, the length of water column in the capillary tube will be:

1. 8cm
2. 6cm
3. 10cm
4. 20cm

On adjusting the P-N junction diode in forward biased

(a) Depletion layer increases	(b) Resistance increases
(c) Both decreases	(d) None of these