Resistance is a measure of a material's ability to impede the flow of electric current. It is measured in ohms (Ω). Power, on the other hand, refers to the rate at which energy is transferred or work is done. It is measured in watts (W).
The resistance of a material can be measured by using an ohmmeter, which applies a small amount of voltage to a circuit and measures the resulting current. The resistance can also be calculated by dividing the voltage by the current, using Ohm's law (R = V/I).
e.m.f stands for electromotive force, and it refers to the voltage or potential difference between two points in a circuit. It is the driving force that causes current to flow through a circuit.
According to Ohm's law, the e.m.f in a circuit is directly proportional to both the current and the resistance. This means that as the resistance increases, the e.m.f required to maintain the same current also increases. Similarly, for a given e.m.f, an increase in resistance will result in a decrease in power.
The resistance of a material depends on its length, cross-sectional area, and the material's resistivity. Power, on the other hand, is affected by the current flowing through the circuit and the resistance of the material. Additionally, the type of material used and the temperature can also affect the resistance and power in a circuit.