In an electric circuit with a resistor of resistance R there is energy conversion to other forms. If there is just one resistor then the voltage drop over the resistor is always equal to the battery voltage drop. But does this mean that the change in potential energy of electrons is totaly converted in the resistor or does some conversion also happen at the pole of the battery where electrons sink? I am thinking of perfect conducting wires. So if you have 1 A and 2 ohms you get that the power consumption is 2 W. Does this mean that the power consumed is 2 W in a resistor? And how is that possible? Shouldn't the battery itself take some of this power where the electrons are being absorbed?


1 Answer 1


It depends on whether you are asking about a real battery or an ideal voltage source.

All real batteries have some internal resistance. In fact they are often modeled as a series combination of a voltage source and a resistance. This resistance causes power loss when current is flowing.

If you had an ideal voltage source (and ideal wires), then all the power would be delivered into the resistor.

Sholdnt the battery itself take some of this power where the electrons are being absorbed?

The ideal voltage source doesn't cause any energy loss. Instead it is the opposite and it raises the potential of the charges in the circuit as they pass the source.

  • $\begingroup$ And what about scenario without any rrsistors? $\endgroup$ Commented Oct 28, 2019 at 9:07
  • $\begingroup$ The power loss you describe is normally only considered for a steady-state circuit. A circuit with a voltage source and no resistance cannot be at steady-state, but has increasing current. The increase cannot continue indefinitely. Eventually the circuit will fail in some manner. (As an example, superconductors have maximum current amounts, above that limit they stop being superconductors, resistance returns and something heats up dramatically from the high current) $\endgroup$
    – BowlOfRed
    Commented Oct 28, 2019 at 9:42
  • $\begingroup$ So in a steady state there is no more increase in kinetic energy and then obviously energy is consumed through the resistance? Something like velocity in air because of resistance when body reaches steady velocity? $\endgroup$ Commented Oct 28, 2019 at 9:50

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