Electricity: Magnetic and Heating Effects - Magnets: Discovery, Poles, and Attraction/Repulsion
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Magnetism was discovered by a shepherd named Magnes in ancient Greece (Magnesia). He found that the iron tip of his staff was attracted to a natural rock called Magnetite ().
Magnetic materials are substances attracted to magnets, such as Iron (), Nickel (), and Cobalt (). Non-magnetic materials include wood, plastic, and gold.
Every magnet has two poles: the North Pole () and the South Pole (). The magnetic force is strongest at these two ends.
A freely suspended magnet always aligns itself in the North-South direction due to the Earth's magnetic field. This property is used in a magnetic compass.
Law of Magnetism: Like poles (e.g., or ) repel each other, while unlike poles (e.g., or ) attract each other.
Magnetic poles always exist in pairs. If a magnet is broken into two pieces, each piece will still have its own North and South pole.
📐Formulae
💡Examples
Problem 1:
A student has two bar magnets. If the South Pole () of the first magnet is brought near the South Pole () of the second magnet, what will be the observation?
Solution:
The two magnets will push away from each other, demonstrating magnetic repulsion.
Explanation:
According to the fundamental law of magnetism, like poles (poles of the same kind) repel each other. Since both poles are South (), they exert a repulsive force.
Problem 2:
If a bar magnet is cut into 3 equal pieces, how many total North poles and South poles will be present?
Solution:
poles and poles (Total of 6 poles).
Explanation:
Magnetic monopoles do not exist. Every time a magnet is divided, each new piece automatically develops its own North () and South () poles. Therefore, 3 pieces result in 3 pairs of poles.
Problem 3:
Why does a magnetic compass needle always point in a specific direction?
Solution:
It aligns with the Earth's magnetic field in the North-South direction.
Explanation:
The Earth behaves like a giant bar magnet. The magnetic compass needle, which is a small magnet, aligns itself with the magnetic field lines of the Earth, pointing towards the geographic North and South.