Which component in a simple circuit tends to oppose sudden changes in current by generating an emf?

Which component in a simple circuit tends to oppose sudden changes in current by generating an emf?

• A. Inductor
• B. Capacitor
• C. Resistor
• D. Transformer

Answer: (A)

An inductor tends to oppose sudden changes in current because it uses its magnetic field to generate an emf when the current changes. When the current through a coil changes, the magnetic flux through the coil changes as well, and Faraday’s law says a voltage is induced that acts to oppose that change. This induced emf is given by V = -L di/dt, where L is the inductance, and the negative sign shows the opposition to the change in current. So rapid increases or decreases in current are resisted, smoothing the current flow. The capacitor resists changes in voltage, not current, by charging or discharging. A resistor just dissipates energy and doesn’t generate an emf to oppose changes in current. A transformer relies on changing currents to transfer energy between windings and isn’t the simple component described here.

An inductor tends to oppose sudden changes in current because it uses its magnetic field to generate an emf when the current changes. When the current through a coil changes, the magnetic flux through the coil changes as well, and Faraday’s law says a voltage is induced that acts to oppose that change. This induced emf is given by V = -L di/dt, where L is the inductance, and the negative sign shows the opposition to the change in current. So rapid increases or decreases in current are resisted, smoothing the current flow. The capacitor resists changes in voltage, not current, by charging or discharging. A resistor just dissipates energy and doesn’t generate an emf to oppose changes in current. A transformer relies on changing currents to transfer energy between windings and isn’t the simple component described here.