Vermogen en energie

Energy is the total work required to drive the current through the circuit.

A rise in voltage results in more work done, passing more current, resulting in increased energy transfer.

Power is the rate at which energy is supplied or absorbed over time, measured in watts.

Power can also be expressed as the product of the instantaneous voltage and current across an element.

The sign of power depends on the current's direction and the polarity of the voltage.

According to the passive sign convention, when the current enters a circuit element at the positive terminal of the voltage and exits the negative terminal, the element absorbs power.

Conversely, if the current enters the negative terminal and exits the positive terminal, the element supplies power.

The total power supplied to the circuit must equal the total power absorbed, validating the energy conservation law.

For an element, the energy absorbed or supplied is the integral of instantaneous power.

If a cassette player draws steady current, then using battery's parameters and power-energy relation, the player's runtime is calculated.