What is the SI unit of power?

State the electric power relation involving current and potential difference.

A passive resistor has current through a potential drop. Does it absorb or supply electrical energy?

A device carries \(3.0\,\mathrm{A}\) with \(12\,\mathrm{V}\) across it. Find its power.

A \(20\,\Omega\) resistor carries \(0.50\,\mathrm{A}\). Find the power dissipated.

A \(60\,\Omega\) resistor has \(120\,\mathrm{V}\) across it. Find its power using \(V^2/R\).

A \(75\,\mathrm{W}\) lamp runs for \(4.0\,\mathrm{h}\). Find the energy used in joules.

A resistor's voltage is doubled while its resistance stays constant. By what factor does the dissipated power change?

A source with emf \(\mathcal E\) and internal resistance \(r\) drives a load \(R\). Derive the power delivered to the load as a function of \(R\).

Using the result for a source with internal resistance, determine the load resistance \(R\) that maximizes load power and find the maximum power.