Why does wire that carries a current become hot?

Answer 1

The wire gets hot because it is too small to carry the rated current. The wire does not have zero impedance (ohms). It may be very, very close to zero, but no wire is truly zero ohms. If you pass a current through a wire of non-zero ohms, you develop a voltage across that wire. (Ohm's law: Voltage = Amps * Ohms) That developed voltage represents power. (Watts = Amps * Voltage) If the power is great enough in comparison to the power dissipation rating of the wire, it gets warm. (Or hot, or melts, or causes a fire, depending on how much power) Typical NEC requirements, which include margins of safety, specify, for instance, that a 15 Amp circuit require a 14 AWG wire, or a 20 Amp circuit require a 12 AWG wire. Try to pass 60 Amps through a 14 AWG wire, which I have actually seen done, and you are just looking for trouble.

Answer 2

A wire becomes hot when the electric current through it is more than the wire was intended for. It happens because wires made from even a good conductor like copper still have resistance, and the power lost in the wire is equal to the resistance times the square of the current.

So as an example a wire of 0.75 mm2 is rated at 6 amps, at which current it gets a bit warm. Putting 12 amps through it would quadruple the power heating the cable and this might melt the insulation or cause a fire risk

Answer 3

The power dissipated by anything when an electric current flows in it is I2R .

' I ' = the current through it, ' R' = its resistance.

-- "Dissipated power" simply means the conductor gets hot. If it gets hot

enough, the conductor can glow, as in a light bulb, or can crisp a nearby slice

of bread, as in an electric toaster.

-- Notice that the dissipated power grows as I2 ... the square of the current.

So twice as much current produces 4-times as much heating, and five-times

the current produces 25-times the heat.

That's why the electromagnet coils in the CAT scan and MRI machines are

chilled in super-cold liquid helium. It turns out that some materials lose all

of their resistance when they get cold enough ... their ' R ' becomes not just

very low, but totally zero, and they can conduct enormous current without

dissipating any power at all. In that condition, they're called "superconductors".

Answer 4

Because it transfers heat and electricity very well. That's why it is used for wiring, but not for cooking. (Yeeouch!!!)

Answer 5

Due to resistance of wire , the power is dissipated in the form of heat, when charge flows through it, so it becomes warm.