Therm-ions are

• photons

• protons

• electrons

• nuclei

Kirchhoff's law of junction, $\mathrm{\Sigma }$I = 0, is based on :

• conservation of energy

• conservation of charge

• conservation of energy as well as charge

• conservation of momentum

353.

If the percentage change in current through a resistor is 1%, then the change in power through it would be:

• 1 %

• 2 %

• 1.7 %

• 0.5 %

3 identical bulbs are connected in series and these together dissipate a power P. If now the bulbs are connected in parallel, then the power dissipated will be:

• P/3

• 3P

• 9P

• P/9

What is the drift velocity of electrons if the current flowing through a copper wire of 1 mm diameter is 1.1 A. Assume that each atom of copper contributes one electron : (Given: density of Cu = 9 g/cm³ and atomic weight of Cu = 63)

• 0.3 mm/s

• 0.5 mm/s

• 0.1 mm/s

• 0.2 mm/s

The equivalent resistance between A and B is

• 10 Ω

• 20 Ω

• 30 Ω

• 49 Ω

An electrical cable of copper has just one wire of radius 9 mm. Its resistance is 5Ω. The single wire of the cable is replaced by 6 different well-insulated copper wires each of radius 3 mm. The total resistance of the cable will now be equal to:

• 270 Ω

• 90 Ω

• 45 Ω

• 7.5 Ω

A current of 2 amperes flowing through a conductor produces 80 joules of heat in ten seconds. The resistance of the conductor is:

• 0.5 Ω

• 2 Ω

• 4 Ω

• 20 Ω

A thermoelectric refrigerator works on

• Joule effect

• Seebeck effect

• Peltier's effect

• Thermionic effect

The potential difference between points A and B is:

• 20/7 V

• 40/7 V

• 10/7 V

• zero