Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Magnetic field does not cause deflection in:

Nuclear forces are

(a) Short ranged attractive and charge independent

(b) Short ranged attractive and charge dependent

(c) Long ranged repulsive and charge independent

(d) Long ranged repulsive and charge dependent

The work done against electrostatic force gets stored in which form of energy?

A small bar magnet of moment M is placed in a uniform field H. If magnet makes an angle of 30° with field, the torque acting on the magnet is

(a) MH

(b)

(c)

(d)

A magnetic dipole of length 10cm has pole strength of 20Am. Find the magnetic moment of the dipole.

A moving coil galvanometer has a resistance of 50 Ω and gives full scale deflection for 10 mA. How could it be converted into an ammeter with a full scale deflection for 1A

(a) 50/99 Ω  in series	(b) 50/99 Ω in parallel
(c) 0.01 Ω in series	(d) 0.01 Ω in parallel

An electron is revolving round a proton, producing a magnetic field of 16 weber/m² in a circular orbit of radius 1Å. It’s angular velocity will be

(a) 1017 rad/sec	(b) 1/2 π  × 1012 rad/sec
(c) 2π × 1012 rad/sec	(d) 4 π × 1012 rad/sec

Charges 4Q, q and Q and placed along x-axis at positions x = 0, x = l/2  and  x = l, respectively. Find the value of q so that force on charge Q is zero             

(a) Q

(b) Q / 2

(c) – Q / 2

(d) – Q

When a photon stimulates the emission of another photon, the two photons have:

Two resistances are connected in two gaps of a metre bridge. The balance point is 20 cm from the zero end. A resistance of 15 ohms is connected in series with the smaller of the two. The null point shifts to 40 cm. The value of the smaller resistance in ohms is

(a) 3

(b) 6

(c) 9

(d) 12