According to Ohm’s Law, a circuit with 40 volts and 8 amps has a resistance of 5 ohms. The calculation uses the rearranged form R = V ÷ I: 40 volts divided by 8 amperes equals 5 ohms.
Ohm’s Law describes the relationship among voltage, current, and resistance in an ohmic circuit. Voltage is the electrical potential difference that drives charge, current is the rate of charge flow, and resistance measures how strongly a component opposes that flow. The complete relationship is V = IR, which can be rearranged to find any one of the three quantities.
The law is named for German physicist Georg Ohm, who published his experimental work on electrical circuits in 1827. A useful qualification is that not every device is ohmic: components such as diodes do not maintain a constant resistance as voltage changes. In a basic quiz problem, however, the stated voltage and current are treated as a steady pair for a resistive circuit, making 5 ohms the single canonical answer.