Question

Why is one of the pins of a three-pin plug relatively thicker?

Hint:

Resistance is inversely proportional to cross-sectional area (\(R = \rho \frac{L}{A}\)).

Answer 1

Step 1: Understanding the Concept:
A three-pin plug has Live, Neutral, and Earth pins.
The top pin is the Earth pin.

Step 2: Detailed Explanation:
The earth pin is made thicker for two main reasons:
1. Safety/Polarity: Being thicker, it physically cannot be inserted into the smaller Live or Neutral holes of a socket, preventing dangerous incorrect connections.
2. Lower Resistance: A thicker pin has a larger cross-sectional area, which translates to lower electrical resistance.
This ensures that in the event of a fault, the fault current easily flows through the earth pin to the ground rather than finding another path.
Additionally, it is usually longer so it makes contact first, ensuring the appliance is earthed before power flows.

Step 3: Final Answer:
It is thicker to provide a low-resistance path for fault currents and to prevent incorrect insertion.