A filament of 500 Ω and its connecting wires of 0.5 Ω in all carry the same 0.4 A…

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

A filament of $500\ \Omega$ and its connecting wires of $0.5\ \Omega$ in all carry the same $0.4\ \text{A}$ . How much heat does each make in one second? Why does only the filament glow?

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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