A resistance R is connected across the terminal of an electric cell of internal resistance 2Ω and the voltage was reduced to 3/5 of its nominal value.
The value of R is
A student is at a height 4m above the ground during a thunderstorm. Given that the potential difference between the thundercloud and the ground is 10\(^7\)V, the electric field created by the storm is
A working electric motor takes a current of 1.5 A when the p.d across it is 250V. If its efficiency is 80%, the power output is
The cost of running five 60 W lamps and four 100 W lamps for 20 hours if electrical energy cost #10.00 per kwh is
