Electric Charges and Fields — Physics STD 12 Science — Question

The coefficient of self inductance of a solenoid is 0.18 mH. If a crode of soft iron of relative permeability 900 is inserted, then the coefficient of self inductance will become nearly

(a)  5.4 mH

(b) 162 mH

(c)  0.006 mH

(d) 0.0002 mH

The deflection in a moving coil galvanometer is

(a) Directly proportional to the torsional constant

(b) Directly proportional to the number of turns in the coil

(c) Inversely proportional to the area of the coil

(d) Inversely proportional to the current flowing

The contact angle between as solid and a liquid is a property of:

1. The material of the solid.
2. The material of the liquid.
3. The shape of the solid.
4. The mass of the solid.

An electron initially at rest, is accelerated through a potential difference of 200 volt, so that it acquires a velocity 8.4 . The value of e/m of electron will be

(a) 2.76

(b) 1.76

(c) 0.76

(d) None of these

Suppose the pressure at the surface of mercury in a barometer tube is P₁ and the pressure at the surface of mercury in the cup is P_2,

1. P₁ = 0, P₂ = atmospheric pressure.
2. P₁ = atmospheric pressure P₂ = 0
3. P₁ = P₂ = atmospheric pressure.
4. P₁ = P₂ = 0

The potential difference applied to an X-ray tube is 5kV and the current through it is 3.2 mA. Then the number of electrons striking the target per second is

(a) 2

(b) 5

(c) 1

(d) 4

The photoelectric effect proves that light consists of :

In a diode AM-detector, the output circuit consist of R = 1kW and C = 10 pF. A carrier signal of 100 kHz is to be detected. Is it good

(a) Yes	(b) No
(c) Information is not sufficient	(d) None of these

The change in frequency due to Doppler effect does not depend on:

1. The speed of the source.
2. The speed of the observer.
3. The frequency of the source.
4. Separation between the source and the observer.

A point positive charge is brought near an isolated conducting sphere. The electric field is best given by: