Magnetism And Matter — Physics STD 12 Science — Question

A change of 0.8 mA in the anode current of a triode occurs when the anode potential is changed by 10 V. If m = 8 for the triode, then what change in the grid voltage would be required to produce a change of 4 mA in the anode current

(a) 6.25 V

(b) 0.16 V

(c) 15.2 V

(d) None of these

At the time of total solar eclipse, the spectrum of solar radiation would be

(a) A large number of dark Fraunhofer lines

(b) A less number of dark Fraunhofer lines

(c) No lines at all

(d) All Fraunhofer lines changed into brilliant colours

Zener diode works on:

When a current in a circular loop is equivalently replaced by a magnetic dipole:

1. The pole strength m of each pole is fixed.
2. The distance d between the poles is fixed.
3. The product md is fixed.
4. None of the above.

A semiconductor is cooled from   to  Its resistance

(a) Will decrease

(b) Will increase

(c) Will first decrease and then increase

(d) Will not change

A charge q is located at the centre of a cube. The electric flux through any face is

(a)

(b)

(c)

(d)

The temperature coefficient of resistance for a wire is 0.00125/℃. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is

(a) 1154 K

(b) 1100 K

(c) 1400 K

(d) 1127 K

The current in a simple series circuit is 5.0 amp. When an additional resistance of 2.0 ohms is inserted, the current drops to 4.0 amp. The original resistance of the circuit in ohms was

(a) 1.25

(b) 8

(c) 10

(d) 20

Which of the following quantities do not depend on the choice of zero potential or zero potential energy?

1. Potential at a point.
2. Potential difference between two points.
3. Potential energy of a two-charge system.
4. Change in potential energy of a two-charge system.

Identify the correct statement from below: