EasyPhysicsHigh School (9–10)Electricity & Magnetism › Current ElectricityNumerical

A heater coil has a resistance of 40 Ω and carries a current of 2.5 A.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A heater coil has a resistance of $40\ \Omega$ and carries a current of $2.5\ \text{A}$ . How much heat does it produce in $15\ \text{s}$ ?

Need a reminder? The key ideaShow

Joule's law: $H = I^2 R t = VIt = \dfrac{V^2}{R}\,t$ . Power $P = VI = I^2 R = \dfrac{V^2}{R}$ , in watts. A fuse, in the live wire, melts when the current is too large.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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