Electricity: Magnetic and Heating Effects - Magnetic Effect of Electric Current (Electromagnets)
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Magnetic Effect of Current: When an electric current passes through a wire, it behaves like a magnet. This was first observed by Hans Christian Oersted using a magnetic compass.
Electromagnet: A coil of insulated wire wound around a magnetic core (usually soft iron) that acts as a magnet only when an electric current flows through it.
Temporary Nature: Unlike permanent magnets, electromagnets are temporary. They lose their magnetism as soon as the electric current is switched 'OFF'.
Strength Factors: The magnetic strength of an electromagnet can be increased by increasing the number of turns in the coil or by increasing the amount of current flowing through the circuit.
Applications: Electromagnets are used in electric bells, cranes to lift heavy iron scrap, telegraphs, and in separating magnetic materials from junk.
📐Formulae
💡Examples
Problem 1:
A student builds an electromagnet using a battery and turns of wire. If they want to make the electromagnet stronger to lift heavier iron nails, what two changes can they make?
Solution:
- Increase the number of turns to or more. 2. Use a stronger power source or add another battery in series.
Explanation:
The magnetic field strength is directly proportional to the number of turns () and the current (). Increasing either will increase the lifting capacity.
Problem 2:
Why is a magnetic compass placed near a current-carrying wire deflected from its North-South position?
Solution:
The deflection is due to the magnetic effect of electric current.
Explanation:
Electric current flowing through a conductor creates a magnetic field around it. This field exerts a force on the compass needle (which is a small magnet), causing it to deflect from its original orientation.
Problem 3:
Identify the core material usually used in an electromagnet and why.
Solution:
Soft Iron core.
Explanation:
Soft iron is used because it magnetizes quickly when current is 'ON' and demagnetizes almost completely when the current is 'OFF', making the electromagnet easy to control.