Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
When an electric current flows through a wire, the wire gets hot. This is known as the Heating Effect of Electric Current.
The amount of heat produced in a wire depends on three main factors: the material of the wire, its length, and its thickness.
Appliances like electric irons, toasters, room heaters, and geysers contain a coil of wire called an element. When current flows through the element, it becomes red hot and gives out heat.
An Electric Fuse is a safety device based on the heating effect. It contains a wire that melts and breaks the circuit if the current exceeds a safe limit, preventing fires and damage to appliances.
In a fuse, the wire is made of a material that has a low melting point so that it breaks the circuit quickly when (heat) increases significantly.
📐Formulae
💡Examples
Problem 1:
Why does the coil (element) of an electric heater glow red, but the connecting cord does not?
Solution:
The element is made of a material like Nichrome with high resistance (), while the cord is made of copper with very low resistance.
Explanation:
According to the formula , more heat is produced in the part of the circuit with higher resistance. Thus, the element gets hot enough to glow, while the connecting cord remains cool.
Problem 2:
If an electric fuse is rated for , what happens if a current of flows through it?
Solution:
The fuse wire will melt and break the circuit.
Explanation:
Because heat produced increases with the square of the current (), the heat generated by will be four times greater than at . This excessive heat melts the fuse wire to ensure safety.