Electric Charges and Fields — Physics STD 12 Science — Question

A heating coil can heat the water of a vessel from 20℃ to 60℃  in 30 minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now will be (neglecting thermal capacity of the coils)

(a) 60 minutes

(b) 30 minutes

(c) 15 minutes

(d) 7.5 minutes

A short bar magnet with its north pole facing north forms a neutral point at P in the horizontal plane. If the magnet is rotated by 90^o in the horizontal plane, the net magnetic induction at P is (Horizontal component of earth’s magnetic field = )

(a) 0

(b) 2

(c)

(d)

What is immaterial for an electric fuse wire

(a) Its specific resistance	(b) Its radius
(c) Its length	(d) Current flowing through it

If a proton and anti-proton come close to each other and annihilate, how much energy will be released

(a) 1.5

(b) 3

(c) 4.5

(d) None of these

The maximum velocity of an electron emitted by light of wavelength λ  incident on the surface of a metal of work function ∅,  is (Where h = Planck's constant, m = mass of electron and c = speed of light.)

(a)

(b)

(c)

(d)

In insulators________. (C.B is conduction band and V.B is valence band)

To get three images of a single object, one should have two plane mirrors at an angle of

(a) 30°

(b) 60°

(c) 90°

(d) 150°

In the given figure, conducting rod AB is moved in the direction of magnetic field developed by the current carrying conductor MN. The direction of generated induced current will be:

Which of the following mirrors is used in searchlight?