Electric Charges and Fields — Physics STD 12 Science — Question

A capacitor is kept connected to the battery and a dielectric slab is inserted between the plates. During this process

(a) No work is done

(b) Work is done at the cost of the energy already stored in the capacitor before the slab is inserted

(c) Work is done at the cost of the battery

(d) Work is done at the cost of both the capacitor and the battery

Which of the following does not fit into a group:

A metal block is exposed to beams of X-ray of different wavelength. X-rays of which wavelength penetrate most

(a) 2 Å

(b) 4 Å

(c) 6 Å

(d) 8 Å

Two capacitors   and   in series, are connected in parallel to a third capacitor. This arrangement is then connected to a battery of e.m.f. = 2V, as shown in the figure. How much energy is lost by the battery in charging the capacitors

(a) 22

(b) 11

(c)

(d)

In two separate set - ups of the Young's double slit experiment, fringes of equal width are observed when lights of wavelengths in the ratio 1 : 2 are used. If the ratio of the slit separation in the two cases is 2 : 1, the ratio of the distances between the plane of the slits and the screen in the two set - ups is

(a) 4 : 1

(b) 1 : 1

(c) 1 : 4

(d) 2 : 1

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

Two samples A and B are initially kept in the same state. Sample A is expanded through an adiabatic process and the sample B through an isothermal process. The final volumes of the samples are the same. The final pressures in A and B are p_A and p_B respectively.

1. p_A > p_B
2. p_A = p_B
3. p_A < p_B
4. The relation between p_A and p_B cannot be deduced.

In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit:

1. Produces less diffraction.
2. Increases intensity.
3. Allows only one colour at a time.
4. Allows a more parallel beam when it passes through the lens.

Which of the following of a radioactive material is a measure of its instability?