Magnetism And Matter — Physics STD 12 Science — Question

The electric intensity  E, current density j  and specific resistance k are related to each other by the relation

(a) E = j/k

(b) E = jk

(c) E = k/j

(d) k = jE

A negative charge is located in the uniform electric field between two plates (not shown).
Where in the diagram will the electron have the greatest change in potential energy before hitting the one of the plates?

Consider the situation of figure. The work done in taking a point charge from P to A is W_A, from P to B is W_B and from P to C is W_C.

1. W_A < W_B < W_C
2. W_A > W_B > W_C
3. W_A = W_B = W_C
4. None of these.

A charge of Q coulomb is placed on a solid piece of metal of irregular shape. The charge will distribute itself

(a) Uniformly in the metal object

(b) Uniformly on the surface of the object

(c) Such that the potential energy of the system is minimised

(d) Such that the total heat loss is minimised

An inductor, a resistor and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance.

Two lenses are placed in contact with each other and the focal length of combination is 80 cm. If the focal length of one is 20 cm, then the power of the other will be

(a) 1.66 D

(b) 4.00 D

(c) –1.00 D

(d) – 3.75 D

The SI unit of electric flux is:

Referring to the figure below, the effective resistance of the network is

(a) 2 r

(b) 4 r

(c) 10 r

(d) 5r/2

Lorentz force is given by the formula:

A cell is connected between two points of a uniformly thick circular conductor. The magnetic field at the centre of the loop will be (Here  and  are the currents flowing in the two parts of the circular conductor of radius ‘a’ and  has the usual meaning)

(a) Zero

(b)  (

(c) (

(d) (