Electric Charges and Fields — Physics STD 12 Science — Question

Two free parallel wires carrying currents in opposite direction

(a) Attract each other

(b) Repel each other

(c) Neither attract nor repel

(d) Get rotated to be perpendicular to each other

If three bulbs 60W, 100W and 200W are connected in parallel, then

(a) 200 W bulb will glow more	(b) 60 W bulb will glow more
(c) 100 W bulb will glow more	(d) All the bulbs will glow equally

If the external force acting on a system have zero resultant, the centre of mass:

1. Must not move.
2. Must not accelerate.
3. May move.
4. May accelerate.

The north pole of a magnet is brought near a stationary negatively charged conductor. What is the force experienced by it at the poles?

 A normal eye is not able to see objects closer than 25cm because:

1. The focal length of the eye is 25cm.
2. The distance of the retina from the eye-lens is 25cm.
3. The eye is not able to decrease the distance between the eye-lens and the retina beyond a limit.
4. The eye is not able to decrease the focal length beyond a limit.

Electron and proton beams are travelling parallel to each other in the same direction. There will be ___________ between them.

The impurity atoms with which pure silicon may be doped to make it a p-type semiconductor are those of:

A thin equiconvex lens is made of glass of refractive index 1.5 and its focal length is 0.2 m, if it acts as a concave lens of 0.5 m focal length when dipped in a liquid, the refractive index of the liquid is

(a)

(b)

(c)

(d)

Hydrogen atom does not emit X-rays because

(a) Its energy levels are too close to each other

(b) Its energy levels are too apart

(c) It is too small in size

(d) It has a single electron

 The formula for electrostatic potential is _____________.