To maintain the current in an inductor, the applied alternating voltage must be:
Correct answer: B. Greater than back emf
- A. Smaller than back emf
- B. Greater than back emf
- C. Equal to back emf
- D. None of these
Explanation
When an alternating voltage is applied to an inductor, it induces a changing magnetic field, which in turn generates a back electromotive force (emf) that opposes the change in current. To maintain or increase the current in the inductor, the applied voltage must exceed this back emf. If the applied voltage is smaller than the back emf, the inductor will act to oppose the change in current, resulting in a decrease in current over time. However, if the applied voltage is greater than the back emf, it effectively overcomes the opposition from the inductor, allowing the current to be maintained or increase.Therefore, to maintain the current in an inductor, the applied alternating voltage must be greater than the back emf generated by the inductor.
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About Alternating Current
Alternating current varies periodically, so phase relationships become essential when current passes through a resistor, capacitor or inductor. The chapter distinguishes resistance from capacitive and inductive reactance, explains phase lead and lag, and connects changing electric and magnetic fields with the production and properties of electromagnetic waves.
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