Power dissipated by a resistor
Learning objectives
- To know the relationships between power (P), voltage (V) and current intensity (I).
- To understand that resistance allows for the control of current intensity and therefore the power dissipated in a circuit.
The circuit is made up of a variable power supply, a variable resistor R and, a light bulb all connected in series.
An ammeter, placed in series, allows the current, I, to be measured. A voltmeter connected in parallel with the resistor, R, allows the voltage across the resistor VR to be measured.
The light bulb acts like a resistor, RA, with resistance equal to 10Ω.
The curve shows the power dissipated in the the resistor. The unit of power is the Watt (W).
P = VR x I = R x I2
- When the voltage is increased, the current, I, increases and the power dissipated by the resistor, R, increases.
- When the value of the resistor is increased, I decreases and the power dissipated by the resistor, R, decreases.
The variable resistor, R, allows control of the current intensity in the circuit.
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