How Does the proximity Effect increase the AC resistance?

Proximity Effect

When the two nearby conductor carries a current, a magnetic field is set up around the conductor. The flux produced by one conductor gets linked to the other conductor and produces an eddy current around the conductor which results in an apparent increase in the resistance of the conductor. The phenomenon is known as the PROXIMITY EFFECT.

The current distribution in the conductor changes because of the proximity effect. The current tends to concentrate away from the center of the conductor. This leads to a decrease in the apparent cross-section area of the conductor.

The current distribution in the conductors when the current flows in the same direction is as given below.





The current concentrate away from the center of both the conductors when the current flows in the same direction. Thus, the apparent area of the conductor reduces, and conductor resistance increase. If the frequency of the current is higher the current tends to concentrate farther from the center and the resistance of the conductor increase. 

The current distribution in the conductors when the current flows in the opposite direction is as given below.



This case has similar effects but the current concentrates at the adjacent sides of the conductor. However, with this current, the resistance increases because of the reduction in the apparent area of the conductors. 

In the case of the DC, the SKIN EFFECT and PROXIMITY EFFECT are totally absent. 


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The proximity effect refers to the increase in AC resistance of a conductor when it is placed in close proximity to another conductor. The phenomenon is caused by the interaction of the electromagnetic fields generated by the alternating current in each conductor. The proximity effect can be quantified using the skin effect, which states that the AC resistance of a conductor is directly proportional to the square root of the frequency of the alternating current and inversely proportional to the conductor's radius.

Formally, the AC resistance of a conductor due to proximity effect can be calculated using the following formula:

AC resistance = (4 * ρ * frequency * length) / (π * radius)

Where:

ρ is the resistivity of the conductor material
frequency is the frequency of the alternating current
length is the length of the conductor
radius is the radius of the conductor

The proximity effect can be mitigated by using thicker conductors, which have a larger radius and therefore less surface area for the electromagnetic fields to interact with.

It can also be mitigated by using a conductor with a higher electrical conductivity, which means lower resistivity, as it will have less resistance to the current flow.