81.

The force between two parallel current carrying wires is independent of

• their distance of separation

• the length of the wires

• the magnitude of currents

• the radii of the wires

The graph between resistivity and temperature, for a limited range of temperatures, is a straight line for a material like

• copper

• nichrome

• silicon

• mercury

In the circuit shown, the current through the 5 Ω resistor is

• $\frac{8}{3} \mathrm{A}$

• $\frac{9}{13} \mathrm{A}$

• $\frac{4}{13} \mathrm{A}$

• $\frac{1}{3} \mathrm{A}$

A 100 W bulb produces an electric field of 2.9 Vm^-1 at a point 3 m away. If the bulb is replaced by 400 W bulb without distributing other conditions, then the electric field produced at the same point is

• 2.9 Vm^-1

• 3.5 Vm^-1

• 5 Vm^-1

• 5.8 Vm^-1

In the given circuit the current through the battery is

• 0.5 A

• 1 A

• 1.5 A

• 2 A

In the circuit shown, the current through 8 Ω is same before and after connecting E. The value of E is

• 12 V

• 6 V

• 4 V

• 2 V

An electric bulb rated 500 W at 100 V is used in a circuit having a 200 V supply. The resistance R that must be put in series with the bulb, so that the bulb draws 500 W is

• 10 Ω

• 15 Ω

• 20 Ω

• 25 Ω

Two copper wires have their masses in the ratio 2 : 3 and the lengths in the ratio 3 : 4.The ratio of their resistances is

• 4 : 9

• 27 : 32

• 16 : 9

• 27 : 128

Two different conductors have same resistance at 0°C. It is found that the resistance of the first conductor at t₁°C is equal to the resistance of the second conductor at t₂°C. The ratio of the temperature coefficients of resistance of the conductors, $\frac{{\mathrm{\alpha }}_1}{{\mathrm{\alpha }}_2}$ is

• $\frac{{\mathrm{t}}_1}{{\mathrm{t}}_2}$

• $\frac{{\mathrm{t}}_2 - {\mathrm{t}}_1}{{\mathrm{t}}_2}$

• $\frac{{\mathrm{t}}_2 - {\mathrm{t}}_1}{{\mathrm{t}}_1}$

• $\frac{{\mathrm{t}}_2}{{\mathrm{t}}_1}$

In the given circuit diagram the current through the battery and the charge on the capacitor respectively in steady state are

• 1 A and 3 µC

• 17 A and 0 µC

• 11 A and 3 µC

• 6 A and 0 µC