Magnetism And Matter — Physics STD 12 Science — Question

A potentiometer is an ideal device of measuring potential difference because

(a) It uses a sensitive galvanometer

(b) It does not disturb the potential difference it measures

(c) It is an elaborate arrangement

(d) It has a long wire hence heat developed is quickly radiated

S.I. unit of electric depole moment is :

Which one of the following has the shortest wavelength?

 When electron remains between orbits, its momentum is:

Two short magnets of equal dipole moments M are fastened perpendicularly at their centre (figure). The magnitude of the magnetic field at a distance d from the centre on the bisector of the right angle is:

Some electric bulbs are connected in series across a 220 V supply in a room. If one bulb is fused then remaining bulbs are connected again in series across the same supply. The illumination in the room will

(a) Increase

(b) Decrease

(c) Remains the same

(d) Not continuous

Two non ideal batteries are connected in series. Consider the following statements
(A) The equivalent emf is larger than either of the two emfs.
(B) The equivalent internal resistance is smaller than either of the two internal resistances.

The frequency and work function of an incident photon are n and . If n_­0 is the threshold frequency then necessary condition for the emission of photo electron is

(a)

(b) v =

(c)

(d) None of these

Consider two waves passing through the same string. Principle of superposition for displacement says that the net displacement of a particle on the string is sum of the displacements produced by the two waves individually. Suppose we state similar principles for the net velocity of the particle and the net kinetic energy of the particle. Such a principle will be valid for:

1. Both the velocity and the kinetic energy.
2. The velocity but not for the kinetic energy.
3. The kinetic energy but not for the velocity.
4. Neither the velocity nor the kinetic energy.

A rectangular coil 20 cm × 20 cm  has 100 turns and carries a current of 1 A. It is placed in a uniform magnetic field       B  = 0.5 T with the direction of magnetic field parallel to the plane of the coil. The magnitude of the torque required to hold this coil in this position is

(a) Zero

(b) 200 N-m

(c) 2 N-m

(d) 10 N-m