Model Paper 3 — Physics STD 12 Science — Question

Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction   is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to

(a)

(b)

(c)

(d)

A pure semiconductor behaves slightly as a conductor at

(a) Room temperature	(b) Low temperature
(c) High temperature	(d) Both (b) and (c)

For one electron vacancy,

If the distance between H and Cl in HCl molecule is 1.28 A, then the value of electric dipole moment of this molecule will be (in Coulomb-meter):

Which of the following materials has a negative temperature coefficient of resistance?

An e.m.f. of 100 millivolts is induced in a coil when the current in another nearby coil becomes 10 ampere from zero in 0.1 second. The coefficient of mutual induction between the two coils will be

(a) 1 millihenry

(b) 10 millihenry

(c) 100 millihenry

(d) 1000 millihenry

The activity of a sample is 64 × 10^–5 Ci. Its half-life is 3 days. The activity will become 5 × 10^–6 Ci after

(a) 12 days

(b) 7 days

(c) 18 days

(d) 21 days

Identify which of the following should be used for polarised light waves?
I. Sunglasses
II. Remove ultraviolet light
III. Reveal stress patterns

Assertion : Short wave bands are used for transmission of ratio waves to a large distance

Reason    : Short waves are reflected by ionosphere

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

Average energy stored in a pure inductance L when a current i flows through it, is

(a)

(b)

(c)

(d)