PHYSICS · Single correct · CBSE · Physics · Magnetic Effects of Electric Current · Magnetic Effects of Electric Current
Problem
During Ørsted’s experiment, the compass needle shows no deflection when the key in the circuit is open. Which of the following is the correct reason?
(a) The magnetic field lines produced by the circuit are broken by the air gap at the open key, so they cannot reach the compass.
(b) A minute current still flows, but the magnetic field it produces is too weak compared with Earth’s field to deflect the compass needle.
(c) No electric current flows through the wire, so no magnetic field is produced around the conductor.
(d) Opening the key makes the wire’s resistance zero, so no heat—and therefore no magnetic field—is generated to deflect the compass.