CBSE
Multiple Choice QuestionsA wire of radius r has resistance R. If it is streched to a radius of . Its resistance becomes
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
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 drift velocity offree electrons in a conductor is vd, when the current i is flowing in it. If both the radius and current are doubled, the drift velocity will be
Vd
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
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
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
The total current supplied to the circuit by the battery is
1 A
2 A
4 A
5 A
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
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
