The correct answer is C. Resistance of heater coil is more than the supply wires.
When current flows through a conductor, it causes the conductor to heat up. The amount of heat generated is proportional to the square of the current and the resistance of the conductor. The resistance of a conductor is determined by its length and cross-sectional area. The longer and thinner a conductor is, the greater its resistance.
The heater coil is a long, thin wire that is designed to have a high resistance. This allows it to generate a lot of heat when current flows through it. The supply wiring, on the other hand, is a short, thick wire that is designed to have a low resistance. This allows it to carry a lot of current without generating too much heat.
When current flows through the heater coil, it generates a lot of heat. This heat causes the coil to glow. The supply wiring, on the other hand, does not generate enough heat to glow. This is because the supply wiring has a lower resistance than the heater coil.
Here is a more detailed explanation of each option:
- Option A: Current through supply line flows at slower speed. This is not the correct answer because the current through the supply wiring and the heater coil are the same. The current is determined by the voltage and the resistance of the circuit. The voltage is the same in both cases, so the current is also the same.
- Option B: Supply wiring is covered with insulation layer. This is not the correct answer because the insulation layer does not affect the resistance of the wire. The resistance of a wire is determined by its length and cross-sectional area. The insulation layer does not change either of these factors.
- Option C: Resistance of heater coil is more than the supply wires. This is the correct answer because the heater coil is designed to have a high resistance. The supply wiring, on the other hand, is designed to have a low resistance.
- Option D: Supply wires are made of superior material. This is not the correct answer because the material of the wire does not affect its resistance. The resistance of a wire is determined by its length and cross-sectional area. The material of the wire does not change either of these factors.