A student modifies the experiment by replacing the copper wire with a plastic thread between points X and Y, keeping all other conditions unchanged. What will be the expected observation regarding the compass needle and why?
The compass needle will not deflect because plastic does not conduct electricity and thus no magnetic field is produced.
In Oersted's experiment, a copper wire is connected between points X and Y of a circuit; when the key is closed, an electric current flows through the wire and a compass needle placed near it deflects.
The deflection happens because a current-carrying conductor produces a magnetic field around it. The magnetic field is due to the moving charges (the current), not due to the wire material itself.
Plastic is an insulator — it has almost no free electrons, so when a plastic thread replaces the copper wire, the circuit is effectively broken and no current flows between X and Y.
No current means no magnetic field around the thread, so the compass needle continues to point along the Earth's magnetic field (north–south) and shows no deflection.
Higher resistance does not produce a sharper deflection — with no current there is no field at all. Plastic does not create a weaker field; it creates none. Friction between the thread and its support has no magnetic effect on a compass.
Hence, the answer is The compass needle will not deflect because plastic does not conduct electricity and thus no magnetic field is produced.
Similar Questions
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Important Questions from Magnetism
- The magnetic field around a straight current-carrying conductor:
Magnetic field is a quantity that has___________________ .
- The right-hand thumb rule is used to find which of the following?
- How are the magnetic field lines arranged inside a current-carrying solenoid?
- What does it mean when magnetic field lines are drawn closer together in a diagram?
