A resistor is connected across a steady d.c. source and operates at a constant temperature.
(i) Show that the electrical power dissipated in a resistor can be expressed in the alternative forms P=I2R and P=RV2.
(ii) Discuss, with reasoning, which of the three expressions P=VI, P=I2R and P=RV2 is most convenient to use when (a) the current and resistance are known, (b) the voltage and resistance are known, and (c) the current and voltage are known. State one experimental situation for each case.