Science
Mona was doing an experiment with a magnetic compass and a straight current-carrying wire. She observed that as she moved the compass away from the current-carrying wire, the deflection of the compass needle reduced.
(a) Explain why the deflection of the compass needle reduced as Mona moved away the compass needle from the current carrying wire.
(b) Mention one thing that could have changed in the circuit of the wire that could increase the deflection of the needle.
(c) Explain with reason what will be the direction of the magnetic field associated with the wire for the case described by the above figure.
Answer
(a) When an electric current flows through a straight wire, it produces a magnetic field around it and the strength of this magnetic field is inversely proportional to the distance from the wire. Therefore, when Mona moved the compass needle away from the current-carrying wire, the magnetic field at that point became weaker. This reduced the force acting on the compass needle and hence, the deflection of the compass needle also decreased.
(b) As the strength of a magnetic field of a wire is directly proportional to the current flowing through it so a higher current produces a stronger magnetic field around the wire, which causes a greater deflection of the compass needle.
(c) As per the battery connection shown, current is flowing from the top of the wire downwards. Hence, by Right-Hand Thumb rule we get magnetic field to be in the clockwise direction.
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