COMEDK · Physics · 23. Alternating Current
A coil offers a resistance of \(20 \mathrm{~ohm}\) for a direct current. If we send an alternating current through the same coil, the resistance offered by the coil to the alternating current will be :
- A Less than \(20 \Omega\)
- B \(0 \Omega\)
- C Greater than \(20 \Omega\)
- D \(20 \Omega\)
Answer & Solution
Correct Answer
(C) Greater than \(20 \Omega\)
Step-by-step Solution
Detailed explanation
A coil is characterized by its resistance \(R\) and its self-inductance \(L\). When a direct current (DC) flows through the coil, the frequency \(f\) is \(0\), so the inductive reactance \(X_L = 2\pi f L = 0\). Thus, the total impedance \(Z\) for DC is equal to the resistance…
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