Work and power of current

When an electric field moves charges along a conductor it does work; this is called the work of the current. Moving a charge q at voltage U takes the work A = qU, and since I = q/t, A = IUt. The work of the current is directly proportional to the current, the voltage and the time. Using Ohm’s law it can also be written as A = I²Rt and A = U²t/R. The unit of work is the joule: 1 J = 1 V · 1 A · 1 s. The amount of work equals the electrical energy converted into other forms (heat, light, mechanical). The work of the current can be measured with an ammeter, a voltmeter and a clock. Experiments with the mains (220 V) are not allowed — do the calculations in your notebook only.