81.

The potential difference between A and B in the following figure is

      

• 32 V

• 48 V

• 24 V

• 14 V

How many 6 μF, 200 V condensers are needed to make a condenser of 18 µF, 600 V ?

• 9

• 18

• 3

• 27

The total energy stored in the condenser system shown in the figure will be

• 2 μJ

• 4 μJ

• 8 μJ

• 16 μJ

A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it

• increases, thermal velocity of the electron decreases

• decreases, thermal velocity of the electron decreases

• increases, thermal velocity of the electron increases

• decreases, thermal velocity of the electron increases

The charges Q, +q and +q are placed at the vertices of an equilateral triangle of side l. If the net electrostatic potential energy of the system is zero, then Q is equal to

• $- \frac{\mathrm{q}}{2}$

• − q

• $\frac{+ \mathrm{q}}{2}$

• Zero

The charge deposited on 4 µF capacitor in the circuit is

• 6 × 10^-6 C

• 12 × 10^-6 C

• 24 × 10^-6 C

• 36 × 10^-6 C

All capacitors used in the diagram are identical and each is of capacitance C. Then the effective capacitance between the point A and B is

• 1.5 C

• 6 C

• C

• 3C

A capacitor and an inductance coil are connected in separate AC circuits with a bulb glowing in both the circuits. The bulb glows more brightly when

• an iron rod is introduced into the inductance coil

• the number of turns in the inductance coil is increased

• separation between the plates of the capacitor is increased

• a dielectric is introduced into the gap between the plates of the capacitor

Two identical charged spheres of material density ρ, suspended from the same point by inextensible strings of equal length make an angle θ between the strings. When suspended in a liquid of density σ the angle θ remains the same. The dielectric constant K of the liquid is

• $\frac{\mathrm{\rho }}{\mathrm{\rho } - \mathrm{\sigma }}$

• $\frac{\mathrm{\rho } - \mathrm{\sigma }}{\mathrm{\rho }}$

• $\frac{\mathrm{\rho }}{\mathrm{\rho } + \mathrm{\sigma }}$

• $\frac{\mathrm{\rho } + \mathrm{\sigma }}{\mathrm{\rho }}$

In the given network, the valve of C, so that an equivalent capacitance between points A and B is 3 µF, is

• $\frac{1}{5} \mathrm{\mu F}$

• $\frac{31}{5} \mathrm{\mu F}$

• 48 μF

• 36 μF