Question

If an induction coil is open then its L and R become
(A) \[\infty ,0\]
(B) \[0,\infty \]
(C) \[\infty ,\infty \]
(D) \[0,0\]

Answer 1

Hint: Inductor is described as an electric component which is composed of a coil of wire and a core inside it. When current is allowed to flow through the coil, it will produce a magnetic field as a result of which electrical energy is stored in the form of magnetic energy. We will use the basic relation between resistance, current and potential of the inductor to evaluate the value of resistance R.

Complete step by step answer:
If an induction coil is open, then it can be assumed as a short circuit to the direct current. When the storage phase is completed, the inductor current that flows through the inductor will be stable. Also, there will be no self-induced electro-motive force and the value of potential difference across the inductor is zero as it is a short circuit. Hence, the inductor will behave like a connecting wire. We know that the resistance of the inductor is equal to the ratio of voltage and current through it. Hence, the value of resistance is zero and inductance L will become infinite.Therefore, if an induction coil is open then its L and R become infinite and zero respectively. Hence, option (A) is correct.

Note: When an alternating current is allowed to pass through the inductor, it stores the electric energy in the form of magnetic energy, but when we supply a direct current to the inductor, the value of current will not change as a result of which no magnetic flux is created as per Lenz’s law. Hence, an inductor will act as a short circuit when it is connected with a DC supply.