Electric Charges and Fields — Physics STD 12 Science — Question

The capacity of a condenser is 4   farad and its potential is 100 valts. The energy released on discharging it fully will be

(a) 0.02 Joule

(b) 0.04 Joule

(c) 0.025 Joule

(d) 0.05 Joule

Figure shows a horizontal solenoid connected to a battery and a switch. A copper ring is placed on a frictionless track, the axis of the ring being along the axis of the solenoid. As the switch is closed, the ring will:

An electromagnetic wave can be produced when the charge is

The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become

(a) Twice its original value	(b) Four times its original value
(c) Half its original value	(d) One-fourth its original value

Which of the adjoining graphs represents ohmic resistance

(a)

(b)

(c)

(d)

Consider the following two statements A and B and identify the correct choice given in the answers

(A) Duddells thermo-galvanometer is suitable to measure direct current only

(B) Thermopile can measure temperature differences of the order of

(a) Both A and B are true	(b) Both A and B are false
(c) A is true but B is false	(d) A is false but B is true

To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because

(a) Determination of moment of inertia is not needed which minimises the errors

(b) Less observations are required

(c) Comparatively less calculations

(d) All the above

Assertion  : The cloud in sky generally appear to be whitish.

Reason      :  Diffraction due to clouds is efficient in equal measure at all wavelengths.

(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.

The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t = 6 seconds, will be

(a) 400

(b) 300

(c) 200

(d) 150

An electron moving with a velocity of 15ms^-1 enters a uniform magnetic field of 0.2 T, along a direction parallel to the field. What would be its trajectory in this field?