If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes supply voltage. This is called:

• A. Ohmic resistance
• B. Inductive reactance
• C. Capacitive reactance
• D. Magnetic flux

Answer: (B)

Winding a conductor into a coil creates self-inductance, which generates a back EMF that resists any change in current. In an AC circuit, where current continually changes, this back EMF opposes the supply voltage. The measure of that opposition due to inductance is inductive reactance. It depends on frequency and the coil’s inductance, with X_L = ωL, and causes the current to lag the applied voltage by 90 degrees in an ideal inductor.

In contrast, ohmic resistance is in-phase with current and simply dissipates some energy as heat; it doesn’t produce the back EMF that resists changes in current. Capacitive reactance comes from a capacitor and causes current to lead voltage, with its own X_C = 1/(ωC). Magnetic flux is the magnetic field related to the coil, not the impedance term that opposes the supply.