We know that a magnetic compass responds to a magnet placed near it. In this section, we investigate whether an electric current can also influence a magnetic compass, indicating a magnetic effect.
Activity: To observe the magnetic effect of electric current in a coil
Step 1: Take an insulated copper wire, a magnetic compass, an electric cell with holder, and a simple switch.
Step 2: Wind the insulated copper wire into a circular coil of about 5–6 turns.
Step 3: Place the magnetic compass at the centre of the coil on a flat surface.
Step 4: Connect the ends of the coil to the cell and switch to form a complete electric circuit.
Step 5: Keep the switch OFF and note the original north–south direction of the compass needle.
Step 6: Turn the switch ON to allow current to flow through the coil and carefully observe the compass needle.
Observation:
- When the switch is turned ON, the compass needle deflects from its original north–south direction, showing that a magnetic field is produced around the coil due to the flow of electric current.
- The amount of deflection indicates the presence and strength of this magnetic field.
- When the switch is turned OFF, the electric current stops flowing, the magnetic field around the coil disappears, and the compass needle returns to its original direction.
- This behaviour is observed every time the circuit is switched ON and OFF.
Conclusion:
The deflection of the compass needle proves that a current-carrying coil produces a magnetic field around it. The magnetic effect exists only as long as electric current flows through the coil and disappears when the current stops. Hence, electric current can produce magnetism, confirming the magnetic effect of electric current.
A magnetic compass contains a tiny magnet that responds to magnetic fields. When electric current flows through a wire, it creates a magnetic field around it. This magnetic field acts on the compass needle and causes it to deflect. When the current stops flowing, the magnetic field vanishes and the compass needle aligns itself with Earth’s magnetic field again.
A magnetic compass
Magnetic effect of electric current:
The phenomenon in which a current flowing through a conductor produces a magnetic field around it is called the magnetic effect of electric current.
Magnetic field:
The region around a magnet or a current-carrying conductor where its magnetic influence can be detected, such as by the deflection of a compass needle, is called a magnetic field.
Magnetic field around a current-carrying conductor
Scientist behind the discovery:
In 1820, the Danish scientist Hans Christian Oersted discovered that an electric current can produce a magnetic field. While demonstrating an electric circuit, he noticed that a nearby compass needle deflected whenever the circuit was switched on or off. This experiment proved the link between electricity and magnetism, leading to further scientific developments.
Hans Christian Oersted
Applications of magnetic effect of electric current:
- Electromagnets
- Electric bells
- Transformers
- Induction cookers and stoves
- Junkyard cranes
- MRI (Magnetic Resonance Imaging)
- Electric motors
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Fans
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Loudspeakers
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Relays
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Generators
A generator and an MRI machine