Four wires of the same diameter are connected, in turn, between two points maintained at a constant potential difference. Their resistivities and lengths are; ρ and L (wire 1), 1.2ρ and 1.2L (wire 2), 0.9ρ and 0.9L (wire 3) and ρ and 1.5L (wire 4). Rank the wires according to the rates at which energy is dissipated as heat, greatest first,
If voltage across a bulb rated 220V, 100W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is
1 Crore+ students have signed up on EduRev. Have you? Download the App |
A heater coil is rated 100 W, 200 V. It is cut into two idential parts. Both parts are connected together in parallel, to the same source of 200 V. The energy liberated per second in the new combination is
If a current of 1.5 A is maintained in a resistor of 10 Ohm, then the energy dissipated in the resistor in 1 minute will be:
Two 2Ω resistances are connected in parallel in circuit X and in series in circuit Y. The batteries in the two circuits are identical and have zero internal resistance. Assume that the energy transferred to resistor A in circuit X within a certain time is W. The energy transferred to resistor B in circuit Y in the same time will be
Two heaters A and B are in parallel across the supply voltage. Heater A produces 500 kJ in 20 minutes and B produces 1000 kJ in 10 minutes. The resistance of A is 100Ω . If the same heaters are connected in series across the same voltage, the heat produced in 5 minutes will be:
The charge flown through a resistance R in time t varies with time according to Q = at – bt2. The total heat produced in R by the time current becomes zero is :
In the circuit shown in figure heat developed across 2Ω, 4Ω and 3Ωresistances are in the ratio of
In the figure shown the thermal power generated in ' y ' is maximum when y = 4 Ω . Then X is:
An electric heater is designed to operate in 100 V main with a power output of 1000 W. When it is connected to a 25 V source, power output is: