Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Assertion  :   When a magnetic dipole is placed in a non uniform magnetic field, only a torque acts on the dipole.

Reason      : Force would also acts on dipole if magnetic field were uniform.

(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.

When an ideal battery is joined with an external resistance in an electric circuit, a current i flows. through it. If another battery like this battery is joined in parallel with this battery, then the magnitude of current flowing in the battery will become:

Two charge + q  and  -q  are situated at a certain distance.  At the point exactly midway between them

(a) Electric field and potential both are zero

(b) Electric field is zero but potential is not zero

(c) Electric field is not zero but potential is zero

(d) Neither electric field nor potential is zero

In a common emitter transistor, the current gain is 80. What is the change in collector current, when the change in base current is 250 mA

(a) 80  × 250 mA

(b) (250 – 80) mA

(c) (250 + 80) mA

(d) 250/80 mA

The current inside a copper voltameter

(a) Is half the outside value	(b) Is the same as the outside value
(c) Is twice the outside value	(d) Depends on the concentration of

X-rays region lies between

(a) Short radiowave and visible region	(b) Visible and ultraviolet region
(c) Gamma rays and ultraviolet region	(d) Short radiowave and long radiowave

Longitudinal waves cannot:

1. Have a unique wavelength
2. Transmit energy
3. Have a unique wave velocity
4. Be polarized.

The graph between wave number ()  and angular frequency (w) is

(a)

(b)

(c)

(d)

A condenser having a capacity 2.0 micro farad is charged to 200 volts and then the plates of the capacitor are connected to a resistance wire. The heat produced in joules will be

(a) 4

(b) 4

(c) 4

(d) 2

The transfer ratio of a transistor is 50. The input resistance of the transistor when used in the common-emitter configuration is 1 KW. The peak value for an A.C input voltage of 0.01 V peak is

(a) 100 mA

(b) 0.01 mA

(c) 0.25 mA

(d) 500 mA