# Do resistors turn electricity into heat?

When wiring resistors to a battery, it generates heat and in the worst case, sets on fire but when it is used to limit current, for example in series to an LED, do they still generate heat ?

• Do you think resistors know what they are wired to? Commented Jul 26, 2018 at 19:31
• They must do : they have a very good relationship with current and voltage ... :) Commented Jul 26, 2018 at 19:33
• @SolarMike That's why they say "I don't care what I am wired to, I only care about my friends Voltage and Current!" Commented Jul 26, 2018 at 19:34
• A small effort in terms of a search on here would have found you this : electronics.stackexchange.com/q/387826/152903 Commented Jul 26, 2018 at 19:34

Yes. This is really basic physics.

Voltage times current is power, which a resistor turns into heat.

From the above and Ohm's law, you can find the power dissipated by a resistor from its resistance and either the voltage across it or the current thru it. In common units:

W = V A

W = V2 / Ω

W = A2 Ω

where W is power in Watts, V is EMF in Volts, A is current in Amperes, and Ω is resitance in Ohms.

Technically they turn electrical energy into heat energy.

No electrons go missing or get converted into heat, but they carry less energy when they leave the resistor than they did on the way in; that energy has become heat.

This is why they are called resistor because they resist the normal motion of charge carriers, electrons. In other words, they reduce current flow in a circuit, among other uses they have. So one consequence is generation of heat, which, intuitively, turns out to be due to friction between free electrons and atoms.

• Saying a resistor reduces current flow in the general case is a very poor mental model at best, downright wrong at worst. Commented Jul 26, 2018 at 20:00