Electromagnetic Waves — Physics STD 12 Science — Question

What is shape of magnet in moving coil galvanometer to make the radial magnetic field?

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

A convex mirror of focal length f forms an image which is   times the object. The distance of the object from the mirror is

(a) (n – 1)f

(b)

(c)

(d) (n + 1)f

In order to coincide the parabolas formed by singly ionised ions in one spectrograph and doubly ionized ions in the other Thomson’s mass spectrograph, the electric fields and magnetic fields are kept in the ratios 1 : 2 and 3 : 2 respectively. Then the ratio of masses of the ions is

(a) 3 : 4

(b) 1 : 3

(c) 9 : 4

(d) None of these

64 drops each having the capacity C and potential V are combined to form a big drop. If the charge on the small drop is q, then the charge on the big drop will be

(a) 2q

(b) 4q

(c) 16q

(d) 64q

When air in a capacitor is replaced by a medium of dielectric constant K, the capacity

(a) Decreases K times

(b) Increases K times

(c) Increases  times

(d) Remains constant

If the light moving in a straight line bends by a small but fixed angle, it may be a case of:

1. Reflection.
2. Refraction.
3. Diffraction.
4. Dispersion.

36 cells, each of emf 4V are connected in series and kept in a box. The combination shows an emf of 88V on the outside. Calculate the number of cells reversed.

A 220 V A.C. supply is connected between points A and B (Fig.). What will be the potential difference V across the capacitor?

In a hydrogen atom, the distance between the electron and proton is 2.5 . The electrical force of attraction between them will be

(a) 2.8

(b) 3.7

(c) 6.2

(d) 9.1