Current Electricity — Physics STD 12 Science — Question

Which of the following is not reversible

(a) Joule effect

(b) Peltier effect

(c) Seebeck effect

(d) Thomson effect

According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photo electrons from a metal Vs the frequency of the incident radiation gives as straight the whose slope?

A gas behaves more closely as an ideal gas at:

1. Low pressure and low temperature.
2. Low pressure and high temperature.
3. High pressure and low temperature.
4. High pressure and high temperature.

The velocity of light in a medium is half its velocity in air.  If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected,   is

(a) 15o

(b) 30 o

(c) 45 o

(d) 60 o

A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is

(a) 6.62 years

(b) 5 years

(c) 3.2 years

(d) 7 years

The coils of a step down transformer have 500 and 5000 turns. In the primary coil an ac of 4 ampere at 2200 volts is sent. The value of the current and potential difference in the secondary coil will be

(a) 20 A, 220 V

(b) 0.4 A, 22000 V

(c) 40 A, 220 V

(d) 40 A, 22000 V

Two wires A and B of same material and mass have their lengths in the ratio 1 : 2. On connecting them to the same source, the rate of heat dissipation in B is found to be 5W. The rate of heat dissipation in A is

(a) 10W

(b) 5W

(c) 20W

(d) None of these

Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. Assertion (A): Magnetic field is useful in producing parallel beam of charged particle. Reason (R): Magnetic field inhibits the motion of charged particle moving across it.

The total charge of the isolated system is always: