The unit of resistance is Ohm. The inverse of resistivity is called conductivity. Below is a table of resistivity. It depends on the temperature of the conductor. When charges move in a conductor under the influence of electromotive force of a battery, work is done or power is delivered.
P is the same as heat loss per unit time in the resistor R of the circuit.
The following two rules are known as Kirchhoff's laws. Sum of all currents entering a junction must equal sum of currents leaving the junction. In this Loop rue, we may consider a rise in the potential to be positive and a drop in the potential to be negative. The simple electrical instruments that measure currents and voltages, use a principal component called a Galvanometer. Rg that allows a small current to pass through it.