Current Electricity

Ten wires each of resistance 1 Ω are connected in parallel, then total resistance will be

• 10 Ω

• 1 Ω

• 0.1 Ω

• 0.001 Ω

A wire of radius r has resistance R. If it is streched to a radius of $\frac{3\mathrm{r}}{4}$. Its resistance becomes

• $\frac{256 \mathrm{R}}{81}$

• $\frac{81 \mathrm{R}}{256}$

• $\frac{16 \mathrm{R}}{9}$

• $\frac{9 \mathrm{R}}{16}$

A drift velocity offree electrons in a conductor is v_d, when the current i is flowing in it. If both the radius and current are doubled, the drift velocity will be

• $\frac{{\mathrm{V}}_{\mathrm{d}}}{8}$

• $\frac{{\mathrm{V}}_{\mathrm{d}}}{4}$

• $\frac{{\mathrm{V}}_{\mathrm{d}}}{2}$

• V_d

Two bulbs rated 200 W, 220V and 100 W, 220V, are connected in series, combination is connected to 220 V supply. Power consumed by the circuit is

• 8O W

• 67 W

• 76 W

• 65 W

In a potentiometer experiment, the balancing with a cell is at 240 cm. On shunting the cell with a resistance of 2 Ω the balancing length becomes 120 cm. The internal resistance of the cell is

• 0.5 Ω 

• 1 Ω 

• 2 Ω 

• 4 Ω 

The total current supplied to the circuit by the battery is

• 1 A

• 2 A

• 4 A

• 5 A

The current in a wire varies with time as I = 5t² + 2t, where I is in ampere and t is in second. The quantity of charge which has to be passed through a cross-section of wire during the times t = 4 s to t = 6 s is

• 220 C

• 340 C

• 273.34 C

• 280 C

Three resistances of 2 Ω, 3 Ω and 6 Ω are connected in parallel and the combination is connected in series with 2 V battery having internal resistance of 1 Ω . The current in the battery is

• 1 A

• 3 A

• 2 A

• 4 A

An electric cable of copper has just one wire of radius 9 mm with resistance 5 Ω . This single copper wire of cable is replaced by 4 different well insulated copper wires each of radius 3 mm. The total resistance of the cable now will be

• 22.5 Ω

• 45 Ω

• 9 Ω

• 11.25 Ω

A rise of temperature 5°C is observed in a conductor by passing a current. If the current is doubled the rise in temperature will be

• 10°C

• 20°C

• 5°C

• 25°C