Question

DC current can be controlled by which of the following?

• A. Impedance
• B. Resistance
• C. Capacitance
• D. Inductance

Hint:

Remember that capacitors and inductors only oppose changing current, not steady DC current.

Answer 1

The Correct Option is B

Step 1: In a steady direct current circuit, Ohm's law applies directly, current \(I = V / R\), where R is resistance. Increasing resistance always reduces the steady current, and this works for both AC and DC.

Step 2: A capacitor blocks steady DC completely once it is fully charged, no continuous current flows through it in the steady state, so it cannot be used to control a continuous DC current the way a resistor can.

Step 3: An inductor opposes only changes in current. Once a DC current becomes steady, the inductor behaves almost like a plain wire and offers no lasting opposition, so it cannot control steady DC current either.

Step 4: Impedance is a combined idea of resistance and reactance, and reactance itself only exists for alternating, time varying currents. Impedance is not a meaningful tool for describing or controlling constant DC current.

Step 5: So among the given options, only resistance is genuinely useful for controlling steady DC current, and that is the correct answer.