Introduction: It is generally observed that when a conductor is carrying direct current (d.c), this current is uniformly distributed over the whole cross-section of the conductor. However, an alternating current flowing through the conductor does not distribute uniformly, rather it has the tendency to concentrate itself near the surface of the conductor.
Definition: The tendency of alternating current to concentrate near the surface of a conductor is known as skin effect.
Cause: A solid conductor may be thought to be consisting of a large number of strands, each carrying a small part of the current. The inductance of each strand will vary according to its position. Thus, the strands near the center are surrounded by a greater magnetic flux and hence have larger inductance than that near the surface. The higher reactance of inner strands causes the alternating current to flow near the surface of conductor causing skin effect.
Disadvantages: The effective area of cross-section of the conductor through which current flows is reduced. Consequently, the resistance of the conductor is slightly increased when carrying an alternating current.
Factors affecting:
- 1) Nature of material
- 2) Diameter of wire – Skin effect increases with increase in the diameter of wire.
- 3) Frequency – It increase with the increase in frequency.
- 4) Shape of wire – It is less for stranded conductor than the solid conductor.
Skin effect is an important factor taken into account for the design of transmission lines.