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Heating effect of current
Beginner
Joule heating.
H = I²RtCollisions of charge carriers with the lattice convert electrical energy to heat: H = I²Rt (Joule heating). Used in heaters and fuses; wasted in cables.
A 10 A current through a 2 Ω element for 60 s: 12 kJ.
Doubling current quadruples heating.
In more detail
When current flows through a resistor, electrical energy is converted into thermal energy. This Joule heating is used in toasters, kettles and heaters.
Real-world uses
- Electric kettles heat water using Joule heating.
- Fuses melt when Joule heating raises their temperature too high.
- Toasters, hairdryers and kettles all use Joule heating, where the resistance of a wire turns electrical energy into heat.
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Frequently asked questions
Is Joule heating always wanted?
No. In wires it is an unwanted loss, which is why thick cables are used.
How much heat is produced?
Power times time, in joules, equal to I squared R times time.
Why do thick cables not heat up as much?
Thick cables have lower resistance, so less energy is wasted as heat for the same current.
Related topics in Current Electricity & Circuits
Resistors in parallel · Colour code of resistors · Electric power · Electrical energy and cost · EMF and internal resistance · Cells in series and parallel