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Magnetic Effect of Electric Current
- A compass needle is a tiny magnet.
- Place a compass below a wire in a circuit.
- When current flows, the needle deflects from its direction.
- When the current stops, the needle goes back.
- So a current carrying wire acts like a magnet.
Example 1 — Switch ON
- The switch is moved to ON and current flows.
- The compass needle turns away from its direction.
- So the current makes a magnetic effect.
Example 2 — Switch OFF
- The switch is moved to OFF and current stops.
- The compass needle returns to its first direction.
- So the magnetic effect goes away with the current.
Important Points
- The space around a magnet or wire where its effect is felt is a magnetic field.
- The magnetic field disappears when the current stops.
Definition — Magnetic Effect of Electric Current
When electric current flows through a conductor, it makes a magnetic field around it. This is the magnetic effect of electric current.
Definition — Magnetic Field
A magnetic field is the region around a magnet or a current carrying wire where its magnetic effect can be felt.
Materials needed
A magnetic compass.
An electric cell and a cell holder.
Two drawing pins, a safety pin, and cardboard for a switch.
Two nails and two connecting wires.
An electric cell and a cell holder.
Two drawing pins, a safety pin, and cardboard for a switch.
Two nails and two connecting wires.
Procedure
Make a switch with drawing pins and a safety pin.
Fix the longer wire between two nails, slightly above the cardboard.
Join the wire to the cell holder and the switch.
Place the compass below the wire.
Move the switch ON, then OFF, a few times.
Fix the longer wire between two nails, slightly above the cardboard.
Join the wire to the cell holder and the switch.
Place the compass below the wire.
Move the switch ON, then OFF, a few times.
Observation
When current flows, the compass needle deflects. When current stops, the needle returns to its direction.
Explanation
The deflection shows the current carrying wire has a magnetic effect. So electric current and magnetism are linked.
◆ Summary
- Current flows, needle deflects.
- Current stops, needle returns.
- Wire acts like a magnet.
- Electricity and magnetism linked.
🔭 Be a Scientist — Hans Christian Oersted
You made the same discovery as Hans Christian Oersted (1777–1851) in 1820. He was a professor in Denmark.
His discovery
While giving a demonstration, he saw a compass needle deflect whenever a circuit was opened or closed. He checked it carefully and found that electric current makes a magnetic field. He then shared his findings with other scientists.
