Question

How would the current in coil be altered if:
(a) the coil has twice as many turns,
(b) the loop was to move three times as fast?

(A) (a) current becomes twice (b) current remains the same.
(B) (a) wind remains the same (b) current becomes thrice.
(C) (a) current becomes half (b) current becomes one third.
(D) (a) current becomes twice (b) current becomes thrice.

Answer 1

Hint: We all know that when a magnetic field around a coil is altered or a magnetic flux is altered, an emf is induced inside the loop, and it is generally perceived as causing electromotive force. Similarly, if an electric charge flows through the wire, a magnetic field also generates around it.

Complete step by step answer:
Let us suppose there is a magnet and a coil. If there is a relative motion between the coils, then the flux's magnetic lines are associated with the coil changes. If one of the magnet poles is brought towards the coil, then the magnetic flux changes, and an emf is induced inside the coil, and the current starts flowing inside the coil.
Although there is one condition for the current to flow, the circuit must be closed. If the current will start to flow inside the coil, we can see the galvanometer needle's deflection. When the magnet is brought in the opposite direction concerning the previous direction, the needle deflects but in the opposite direction.We must keep in mind that the galvanometer's coil deflection's value is directly proportional to the speed at coil or magnet is moved relative to each other. Hence if the coil will approach the magnet three times faster, the current would also become three times stronger.We also know that the coils current is directly proportional to the number of turns in the coil. Therefore, if the number of turns in the coil will become twice, then the coil's current flowing will also double.
Therefore, the current would become twice and thrice when the number of turns in the coil would be twice, and the coil will move three times fast, respectively, and the correct option is (D).

Note: The direction of the magnetic force responsible for driving the charge is given by right-hand rule. According to this rule, if your index finger represents the direction of the current flow, the middle finger represents the magnetic field's direction. The thumb represents the direction of the magnetic force.