A magnet, when moved near a coil, produces an induced current. Which of the following method(s) can be used to increase the magnitude of the induced current?
(i) Increasing the number of turns in the coil
(ii) Increasing the speed of the magnet
(iii) Increasing the resistivity of the wire of the coil

Correct option is A

The correct answer is (A) Both (i) and (ii).

Explanation:

The magnitude of the induced current in a coil is determined by Faraday's Law of Electromagnetic Induction, which states:

Induced$$EMF \propto \frac{d\Phi}{dt}$$​​

Where:

• Φ = Magnetic flux through the coil
• dΦ/dt = Rate of change of magnetic flux

The factors that increase the magnitude of the induced current are:

1. Increasing the number of turns in the coil (i):
• More turns mean greater total flux linkage (NΦ).
• This increases the induced EMF and hence the current.
2. Increasing the speed of the magnet (ii):
• Faster movement of the magnet increases the rate of change of magnetic flux (dΦ/dt).
• This leads to a stronger induced EMF and current.

Why Option (iii) is Incorrect:

• Increasing the resistivity of the wire of the coil (iii):
• Higher resistivity increases the resistance of the coil, which reduces the induced current according to Ohm’s Law:

​$$I = \frac{\text{EMF}}{R}$$​​

Hence, this does not increase the magnitude of the induced current; it decreases it.