Electricity: Magnetic and Heating Effects - Magnetic Effect of Electric Current: Oersted’s Observation
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
In , Hans Christian Oersted discovered that an electric current flowing through a conducting wire produces a magnetic field around it.
The magnetic effect of electric current is the phenomenon where a magnetic compass needle gets deflected when placed near a wire carrying an electric current ().
The deflection of the compass needle indicates that the current-carrying wire behaves like a magnet.
The direction of the magnetic field depends on the direction of the current flow. If the direction of the current is reversed, the direction of the compass needle's deflection is also reversed.
The strength of the magnetic field produced is directly proportional to the magnitude of the current () passing through the wire.
The magnetic effect decreases as the distance () from the current-carrying conductor increases.
The rule is used to remember the direction of deflection: If current flows from to in a wire held a magnetic needle, the north pole of the needle deflects towards the .
📐Formulae
💡Examples
Problem 1:
A student observes that a compass needle placed near a circuit deflects only when the switch is 'ON'. What happens to the deflection if the battery terminals are reversed?
Solution:
The compass needle will deflect in the opposite direction.
Explanation:
According to Oersted's observation, the direction of the magnetic field depends on the direction of the current. By reversing the battery terminals, the current flow is reversed, causing the magnetic field lines to change direction, which results in the needle deflecting to the opposite side.
Problem 2:
How can the deflection of a magnetic needle be increased without changing the direction of the current in a wire?
Solution:
The deflection can be increased by increasing the current () in the wire or by moving the needle closer to the wire.
Explanation:
The magnetic field strength is directly proportional to the current (). Increasing the voltage or reducing resistance increases , thereby strengthening the magnetic field. Also, since , decreasing the distance increases the magnetic effect felt by the needle.