Current Electricity — Physics STD 12 Science — Question

A beam of ions with velocity 2   enters normally into a uniform magnetic field of 4 If the specific charge of the ion is 5 , then the radius of the circular path described will be

(a) 0.10 m

(b) 0.16 m

(c)  0.20 m

(d) 0.25 m

The decay constant of radium is 4.28  per year. Its half life will be

(a) 2000 years

(b) 1240 years

(c) 63 years

(d) 1620 years

Energy in the sun is generated mainly by

(a) Fusion of radioactive material	(b) Fission of helium atoms
(c) Chemical reaction	(d) Fusion of hydrogen atoms

One end of a metal rod is dipped in boiling water and the other is dipped in melting ice:

1. All parts of the rod are in thermal equilibrium with each other.
2. We can assign a temperature to the rod.
3. We can assign a temperature to the rod after steady state is reached.
4. The state of the rod does not change after steady state is reached.

Which impurity is doped in Si to form N-type semi-conductor?

(a) Al

(b) B

(c) As

(d) None of these

Which of the following is the most suitable material for making permanent magnet?

A proton beam is going from north to south and an electron beam is going from south to north. Neglecting the earth's magnetic field, the electron beam will be deflected

1. Towards the proton beam.
2. Away from the proton beam.
3. Upwards.
4. Downwards.

A person brings a mass of 1kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2ms^-1 as it reaches A. The work done by the person on the mass is -3J. The potential at A is:

1. -3J kg^-1
2. -2J kg^-1
3. -5J kg^-4
4. None of these.

In the circuit shown below, the cell has an e.m.f. of 10 V and internal resistance of 1 ohm. The other resistances are shown in the figure. The potential difference   is

(a) 6 V

(b) 4 V

(c) 2 V

(d) -2V