Current Electricity — Physics STD 12 Science — Question

The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 seconds. Its half life is

(a) 2 seconds

(b) 4 seconds

(c) 5 seconds

(d) 6 seconds

What is the momentum of a photon having frequency 1.5 

(a) 3.3	(b) 3.3
(c) 6.6	(d) 6.6

The impurity atom added to germanium to make it N-type semiconductor is

(a) Arsenic

(b) Iridium

(c) Aluminium

(d) Iodine

When an ammeter is shunted its measuring range :

According to Faraday's law of electromagnetic induction

(a) The direction of induced current is such that it opposes the cause producing it

(b) The magnitude of induced e.m.f. produced in a coil is directly proportional to the rate of change of magnetic flux

(c) The direction of induced e.m.f. is such that it opposes the cause producing it

(d) None of the above

The rate of change of current needed to induce an emf of 8V in 0.1H coil is.

The solar spectrums is :

An electron is moving towards x-axis. An electric field is along y-direction then path of electron is

(a) Circular

(b) Elliptical

(c) Parabola

(d) None of these

The magnetic field due to a short magnet at a point on its axis at distance X cm from the middle point of the magnet is 200 Gauss. The magnetic field at a point on the neutral axis at a distance X cm from the middle of the magnet is

(a) 100 Gauss

(b) 400 Gauss

(c) 50 Gauss

(d) 200 Gauss

A current i ampere flows along the inner conductor of a coaxial cable and returns along the outer conductor of the cable, then the magnetic induction at any point outside the conductor at a distance r metre from the axis is

(a) ∞

(b) Zero

(c)

(d)