, the component. This is achieved using an ammeter in series with the component and a voltmeter in parallel with the component:
Resistance can then be calculated using 'Ohms Law' in which potential difference, current and resistance are related by the equation:
Potential difference (volt, V) = Current (ampere, A) × Resistance (ohm, Ω)
The resistance of a material is closely related to the number of charge carriers. Not only must the charge carrier have a charge, but they must also be able to move. In a metal the charge carrier is a delocalised electron. Metals with more delocalised electrons, have a resistance - this is why different metals have different resistances.
There are special materials, in which the number of charge carries can change. This means they sometimes conduct electricity well, and sometimes they do not. These are known as semiconductors. Two such semiconductors are:
- thermistor (thermal resistor)
- Light depentant resistor (LDR)
