Atoms — Physics STD 12 Science — Question

The dimensions of electric potential are:

The range of a projectile fired at an angle of 15° is 50m. If it is fired with the same speed at an angle of 45°, its range will be:

1. 25m
2. 37m
3. 50m
4. 100m.

Coulomb’s Law is valid for ______?

The same mass of copper is drawn into two wires 1 mm and 2 mm thick. Two wires are connected in series and current is passed through them. Heat produced in the wire is in the ratio

(a) 2 : 1

(b) 1 : 16

(c) 4 : 1

(d) 16 : 1

As the temperature of hot junction of a thermo‑couple is increased (while cold junction is at constant temperature), the thermo e.m.f.

(a) Increases uniformly at constant rate

(b) Increases slowly in the beginning and more rapidly at higher temperatures

(c) Increases more rapidly in the beginning but less rapidly at higher temperatures

(d) In minimum at neutral temperature

Assertion :   Acceleration of a magnet falling through a long solenoid decreases.

Reason     : The induced current produced in a circuit always flow in such direction that it opposes the change or the cause the produced it.

(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 the assertion and reason both are false.

In nuclear fission the percentage of mass converted into energy is about

(a) 10%

(b) 0.01%

(c) 0.1%

(d) 1%

In a nuclear reactor, the fuel is consumed at the rate of 1 mg/s. The power generated in kilowatt is

(a) 9

(b) 9

(c) 9

(d) 9

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

(a) Is the same for all metals and independent of the intensity of the radiation

(b) Depends on the intensity of the radiation

(c) Depends both on the intensity of the radiation and the metal used

(d) Depends on the nature of the metals used

The potential gradient along the length of a uniform wire is 10 volt/metre.  B and C are the two points at 30 cm  and  60 cm point on a meter scale fitted along the wire. The potential difference between B  and  C will be

(a) 3 volt

(b) 0.4 volt

(c) 7 volt

(d) 4 volt