Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Assertion :   Magnetic field interacts with a moving charge and not with a stationary charge.

Reason    : A moving charge produces a magnetic field.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

Consider a wheel of a bicycle rolling on a level road at a linear speed v₀:

1. The speed of the particle A is zero.
2. The speed of B, C and D are all equal to v₀.
3. The speed of C is 2v₀.
4. The speed of B is greater than the speed of O.

Given a point source of light, which of the following can produce a parallel beam of light

(a) Convex mirror

(b) Concave mirror

(c) Concave lens

(d) Two plane mirrors inclined at an angle of 90°

Capacity of a parallel plate condenser can be increased by:

A 10 micro-farad capacitor is charged to 500 V and then its plates are joined together through a resistance of 10 ohm. The heat produced in the resistance is

(a) 500 J

(b) 250 J

(c) 125 J

(d) 1.25 J

Two insulated charged conducting spheres of radii 20 cm and 15 cm respectively and having an equal charge of 10 C  are connected by a copper wire and then they are separated. Then

(a) Both the spheres will have the same charge of 10 C

(b) Surface charge density on the 20 cm  sphere will be greater than that on the 15 cm  sphere

(c) Surface charge density on the 15 cm sphere will be greater than that on the 20 cm  sphere

(d) Surface charge density on the two spheres will be equal

A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An emf is induced in the loop if:

There is a sudden increase in current in zener diode is:

The ratio of the forces between two small spheres with constant charge (a) in air (b) in a medium of dielectric constant K is

(a) 1 : K

(b) K : 1

(c)

(d)

A LC circuit is in the state of resonance. If C = 0.1μF and L = 0.25 henry. Neglecting ohmic resistance of circuit what is the frequency of oscillations

(a) 1007 Hz

(b) 100 Hz

(c) 109 Hz

(d) 500 Hz