<^< Worksheet: Resistors in Parallel | Course Index | Examples: Resistance and Temperature >^>
Graph showing how resistance varies with temperature
The resistance of a conductor at a temperature, t, is given by the equation:
Rt = R0(1 + αt + βt2 + γt3....)
where α, β, γ, etc., are constants and R0 is the temperature at 0°C.
The coefficients, β, γ, etc., are quite small and since we are normally only dealing with a relatively restricted temperature range (e.g., 0°C to 100°C) we can usually approximate the characteristic to a straight line law in which case, the equation simplifies to:
Rt = R0(1 + αt)
where α is known as the temperature coefficient of resistance. Some typical values for α for various materials are given in the table below. Note that α is expressed in Ω/Ω/°C or just °C.
Element | α (°C) |
Platinum | +0.0034 |
Silver | +0.0038 |
Copper | +0.0043 |
Iron | +0.0065 |
Carbon | -0.0005 |
<^< Worksheet: Resistors in Parallel | Course index | Examples: Resistance and Temperature >^>