Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

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

A toroid of n turns, mean radius R and cross-sectional radius a carries current I. It is placed on a horizontal table taken as x-y plane. It's magnetic moment m:

A substance is behaving as convex lens in air and concave in water, then its refractive index is

(a) Smaller than air	(b) Greater than both air and water
(c) Greater than air but less than water	(d) Almost equal to water

Eels are able to generate current with biological cells called electroplaques. The electroplaques in an eel are arranged in 100 rows, each row stretching horizontally along the body of the fish containing 5000 electroplaques. The arrangement is suggestively shown below. Each electroplaques has an emf of 0.15 V and internal resistance of 0.25 W

The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of 500 W, the current an eel can produce in water is about

(a) 1.5 A

(b) 3.0 A

(c) 15 A

(d) 30 A

Binary of decimal number 25 is :

Which law can ampere’s circuital be derived from?

Two identical thin bar magnets each of length l and pole strength m are placed at right angle to each other with north pole of one touching south pole of the other. Magnetic moment of the system is

(a) ml

(b) 2ml

(c)

(d)

Photoelectric effect shows:

When the number of turns per unit length in a solenoid is doubled then its coefficient of self induction will become.

The photoelectric effect can be understood on the basis of: