Question

The current produces heat, then why is it that the lead wires carrying current are cold while the element of the heater is hot?
(A) The element of the heater is hot due to its high resistance, while the lead wires are cold due to its low resistance.
(B) The element of the heater is made up of nichrome which has low resistance as compared to the high resistance of lead wires, thus the element draws more current.
(C) The element of the heater is thick so its resistance is small, hence more current flows through it than the leads.
(D) Due to low resistance the power generated in the heater's coil is more, but is less in lead wires.

Answer 1

Hint
Electrical energy has converted into heat energy. We have to find the factors responsible for lead wire to be cold while the element of heater to be hot. On studying various factors; we will find that resistance was the major factor responsible for different behavior in lead wires and elements.

Complete step by step answer
Current is the rate of flow of electrons.
Lead wires: these are long length wires and are used to connect two electrical points.
Heating element: these are thick coiled elements or folded tubes. It is short in length.
Working of both lead wires and heating elements is based on the principle of Joules law of heating. It states that $P \propto {I^2}R$ where
P= power
I= current
R = resistance.
So, the value of resistance should be small enough compared to current of wire, in order to draw more energy.
Area of the cross section of thick wires is more than thin wires. As area is inversely proportional to resistance from Ohm’s law. This proves that lead wires have small resistance and elements have high resistance.
This is the reason why the element of the heater is hot due to its high resistance, while the lead wires are cold due to its low resistance. Hence the correct solution is option (A).

Note
Heating is not due to maximum resistance. Heating does not depend on the material of wire. If the thickness of substances were to be considered as high resistive material just by viewing the object then we might not reach the solution, we should have a correct knowledge of Ohm's law and Joules law of heating. Else we will get part (C), but this isn’t the correct solution.