Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

The band gap between the valence band and conduction band is the measure of ______?

Compton effect shows that

(a) X-rays are waves	(b) X-rays have high energy
(c) X-rays can penetrate matter	(d) Photons have momentum

3 A of current is flowing in a linear conductor having a length of 40 cm. The conductor is placed in a magnetic field of strength 500 gauss and makes an angle of 30° with the direction of the field. It experiences a force of magnitude

(a) 3

(b) 3

(c) 3

(d) 3

A magnet makes 40 oscillations per minute at a place having magnetic field intensity of 0.1 × 10^–5 T. At another place, it takes 2.5 sec to complete one vibration. The value of earth’s horizontal field at that place is

(a) 0.25 × 10–6 T

(b) 0.36 × 10–6 T

(c) 0.66 × 10–8 T

(d) 1.2 × 10–6 T

A free electron is placed in the path of a plane electromagnetic wave. The electron will start moving:

A convex mirror has a focal length f. A real object is placed at a distance f in front of it from the pole produces an image at

(a) Infinity

(b) f

(c) f/2

(d) 2f

Twelve wires of equal length and same cross-section are connected in the form of a cube. If the resistance of each of the wires is  R, then the effective resistance between the two diagonal ends would be

(a) 2 R

(b) 12 R

(c)

(d) 8 R

A circular loop of area 1cm², carrying a current of 10A, is placed in a magnetic field of 0.1T perpendicular to the plane of the loop. The torque on the loop due to the magnetic field is:

A diminished virtual image can be formed only in

(a) Plane mirror	(b) A concave mirror
(c) A convex mirror	(d) Concave-parabolic mirror

In a Young’s double slit experiment, the source illuminating the slits is changed from blue to violet. The width of the fringes

(a) Increases

(b) Decreases

(c) Becomes unequal

(d) Remains constant