Current Electricity — Physics STD 12 Science — Question

A 10 m long wire of 20W resistance is connected with a battery of 3 volt e.m.f. (negligible internal resistance) and a 10 W resistance is joined to it is series. Potential gradient along wire in volt per meter is

(a) 0.02

(b) 0.3

(c) 0.2

(d) 1.3

If a power of 100 W is being supplied across a potential difference of 200 V, current flowing is

(a) 2 A

(b) 0.5 A

(c) 1 A

(d) 20 A

There is an air filled 1 pF parallel plate capacitor. When the plate separation is doubled and the space is filled with wax, the capacitance increases to 2pF. The dielectric constant of wax is

(a) 2

(b) 4

(c) 6

(d) 8

A planet of mass M has a satellite of mass m, revolving around the planet in a circular orbit of radius r and time period T. The mass (M) of the planet is

(a)

(b)

(c)

(d)

When an electron jumps from its orbit to another orbit, energy is:

When cells are connected in parallel, then

(a) The current decreases	(b) The current increases
(c) The e.m.f. increases	(d) The e.m.f. decreases

A moving coil galvanometer has N number of turns in a coil of effective area A, it carries a current I. The magnetic field B is radial. The torque acting on the coil is

(a)

(b)

(c)

(d) NABI

Assertion  :  The temperature coefficient of resistance is positive for metals and negative for P-type semiconductor. 

Reason     : The effective charge carriers in metals are negatively charged whereas in P-type semiconductor they are positively charged.

(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.

Rydberg’s constant is:

Four cylinders contain equal number of moles of argon, hydrogen, nitrogen and carbon dioxide at the same temperature. The energy is minimum in:

1. Argon.
2. Hydrogen.
3. Nitrogen.
4. Carbon dioxide.