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 wire.
Circuit setup
Step 1: Take an insulated copper wire, a magnetic compass, an electric cell with holder, and a simple switch.
Step 2: Place the magnetic compass near the wire on a flat surface.
Step 3: Connect the ends of the wire to the cell and switch to form a complete electric circuit.
Step 4: Keep the switch OFF and note the original north–south direction of the compass needle.
Step 5: Turn the switch ON to allow current to flow through the wire 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 wire 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 wire 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 wire produces a magnetic field around it. The magnetic effect exists only as long as electric current flows through the wire 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.
Relationship between electricity and magnetism:
Electricity and magnetism are closely related. When electric current flows through a wire, it produces a magnetic field around it. This shows that electricity can create magnetism. The above activity demonstrates that a current-carrying conductor behaves like a magnet and can influence a compass needle. Thus, electricity and magnetism are interconnected phenomena.
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
Deflection of a compass needle near a current-carrying conductor:
- A magnetic compass normally aligns in the north–south direction due to Earth’s magnetic field.
- When a current flows through the nearby wire, a new magnetic field is produced around it.
- This magnetic field interacts with the compass needle and causes it to deflect from its original direction.
- When the current is switched OFF, the magnetic field disappears and the needle returns to its original position.
- This deflection shows the presence of a magnetic field around a current-carrying conductor.
- The strength of the magnetic field depends on the amount of current flowing through the conductor.
Reference:
https://www.electronics-lab.com/article/magnetic-fields-produced-by-electrical-currents/