Two resistances and when connected in series and parallel with 120 V line, power consumed is 25 W and 100 W respectively. Then the ratio of power consumed by to that consumed by is :
1 : 1
1 : 2
2 : 1
1 : 4
A heating coil can heat the water of a vessel from to in 30 minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now is (neglecting thermal capacity of the coils) :
60 minutes
30 minutes
15 minutes
7.5 minutes
Pick out the wrong statement :
In a simple battery circuit, the point of lowest potential is the negative terminal of the battery
The resistance of an incandescent lamp is greater when the lamp is switched off
An ordinary 100 W lamp has less resistance than a 60 W lamp
At constant voltage, the heat developed in a uniform wire varies inversely as the length of the wire used
A steel wire has a resistance twice that of an Aluminium wire. Both of them are connected with a constant voltage supply. More heat is dissipated
in :
Steel wire when both are connected in series
Steel wire when both are connected in parallel
Aluminium wire when both are connected in series
Aluminium wire when both are connected in parallel
If two bulbs of wattage 25 and 30, each rated at 220 volts, are connected in series with a 440 volt supply, which bulb will fuse?
25 W bulb
30 W bulb
Neither of them
Both of them
In the circuit shown below, the power developed in the 6( resistor is 6 watt. The power in watts developed in the 4( resistor is :
16
9
6
4
Two wires A and B of same material and mass have their lengths in the ratio 1 : 2. On connecting them to the same source, the rate of heat dissipation in B is found to be 5W. The rate of heat dissipation in A is :
10W
5W
20W
None of the above
An electric kettle has two heating coils. When one coil is used, water in the kettle boils in 5 minutes, while when second coil is used; same water boils in 10 minutes. If the two coils, connected in parallel are used simultaneously, the same water will boil in time :
3 min 20 s
5 min
7 min 30 s
2 min 30 s
Two electric bulbs rated watt V volts and watt V volts are connected in parallel and V volts are applied to it. The total power is :
An electric iron draws 5 amp, a TV set draws 3 amp and refrigerator draws 2 amp from a 220 volt main line. The three appliances are connected in parallel. If all the three are operating at the same time, the fuse used may be of :
20 amp
5 amp
15 amp
10 amp