Two 220-volt, 100-watt bulbs are connected first in series and then in parallel. Each time the combination is connected to a 220-volt a.c. supply line. The power drawn by the combination in each case respectively will be:
50 watt,100 watt
100 watt,50 watt
200 watt,150 watt
50 watt,200 watt
If rated voltage = supply voltage then use
\(\frac{1}{P}=\frac{1}{P_1}+\frac{1}{P_2}\) (series connection) & P = P1 + P2 (parallel connection)
Two cables of copper are of equal lengths. One of them has a single wire of area of cross-section A, while other has 10 wires of cross-sectional area \(\frac{A}{10}\) each. Give their suitability for transporting A.C. and D.C.
Power is defined as the rate of doing work. Electric power is the rate at which electrical energy is transferred through an electric circuit, i.e. the rate of transfer of electricity. The symbol for Electric Power is ‘P’. SI unit of electric power is Watt.
P = VI
From Ohm's Law, V = IR
Hence, Power can also be expressed as P = I2R