Understanding the Property of a Coil Opposing Current Change

The question asks about a specific property of an electrical coil that causes it to resist or oppose any change in the electric current passing through it. This opposition to the change in current is a fundamental characteristic of inductive components in electrical circuits.

Defining the Inductive Property

When current flows through a coil, it creates a magnetic field around the coil. If the current changes, the magnetic field also changes. According to Faraday's law of electromagnetic induction, a changing magnetic field induces a voltage (electromotive force or EMF) in the coil. Lenz's law further states that the direction of this induced voltage is such that it opposes the very change in current that produced it. This inherent property of a coil to oppose changes in current is known as inductance.

There are two main types of inductance:

• Self-inductance: This is the property of a single coil where a change in the current flowing through the coil induces a voltage within that same coil, opposing the current change. The question describes this exact phenomenon.
• Mutual inductance: This is the property where a change in current in one coil induces a voltage in a nearby second coil. This involves the interaction between two separate inductive components.

Analyzing the Options

• Mutual - inductance: As explained above, mutual inductance involves the interaction between two coils, not the property of a single coil opposing its own current change. Therefore, this option is incorrect.
• Self - inductance: This term precisely matches the definition given in the question – the property of a coil opposing the change of current flowing through it.
• Toroidal inductor: This refers to a specific physical shape of an inductor (a coil wound on a ring-shaped core). It is a type of inductor, not a fundamental property like inductance. Therefore, this option is incorrect.
• Air Core inductor: This refers to a type of inductor where the core material is air (or non-magnetic material). It describes the construction of an inductor, not the property of opposing current change. Therefore, this option is incorrect.

Based on the definitions and analysis, the property described is self-inductance.

The induced voltage ($$V$$) across an inductor due to the change in current ($$\frac{dI}{dt}$$) flowing through it is given by the formula:

$$V = -L \frac{dI}{dt}$$

Where $$L$$ is the self-inductance of the coil, measured in Henrys (H).

Self-Inductance Explained Further

The value of self-inductance ($$L$$) depends on the physical characteristics of the coil, such as the number of turns, the area of the coil, the length of the coil, and the permeability of the core material. A higher self-inductance means the coil will produce a larger opposing voltage for the same rate of change of current.

Revision Table: Key Inductance Concepts

Additional Information: Related Principles

Understanding self-inductance is closely tied to fundamental laws of electromagnetism:

• Faraday's Law of Induction: States that a changing magnetic flux through a circuit induces an electromotive force (voltage) in the circuit. In the case of self-inductance, the changing magnetic flux is caused by the coil's own changing current.
• Lenz's Law: Specifies the direction of the induced current or voltage. It states that the induced EMF opposes the change in magnetic flux that produced it. This is why the induced voltage in an inductor opposes the change in current.
• Unit of Inductance: The standard unit for both self-inductance and mutual inductance is the Henry (H). One Henry is defined as the inductance of a circuit in which an EMF of one volt is induced when the current is changing at the rate of one ampere per second.