Test: Faraday’s Laws of Induction - JEE MCQ

When a magnet is moved towards the coil quickly, the rate of change of flux is larger than that if the magnetic field is moved slowly, thus larger emf is induced due to quick movement of the coil.

Change n in magnetic flux Δϕ=0.1−1=−0.9 Weber
Time taken  Δt=0.1 sec
So, emf induced in the coil  E=− Δϕ​/Δt
⟹ E=− (−0.9)​/ 0.1=9 Volts
Hence option C is the correct answer.

In hydroelectricity the power of a turbine depends on the size of the water drop and the quantity of water flowing through the turbine. The water propels the turbine, which in turn powers an electric generator, which produces electricity under the principle of electromagnetic induction.

Lenz’s law is used for determining the direction of induced current.
Lenz’s law of electromagnetic induction states that the direction of induced current in a given magnetic field is such that it opposes the induced change by changing the magnetic field.
Following is the formula of Lenz’s law:
ϵ=−N (∂ϕ_B/∂t)
Where,

• ε is the induced emf
• ∂ΦB is the change in magnetic flux
• N is the number of turns in the coil
   

Lenz’s law finds application in electromagnetic braking and in electric generators

The negative sign signifies that the induced emf always opposes any change in the magnetic flux.

= 4t-3
At t = 0.25s
e= 2V

According to Lenz’s law the end A becomes the North Pole to oppose the motion of the magnet.
Hence, option B is correct.
 

This is because induced emf directly depends on relative motion between the magnet and coil, but if there is no relative motion between them, there will be no emf induced.

Self induction is that phenomenon in which a change in electric current in a coil produces an induced emf in the coil itself.
Now, it is also known as inertia of electricity as for if we were to change electric current through a current carrying coil it will tend to oppose any further change in its emf. This is similar to inertial behavior in mechanics where bodies in either rest or motion tend to oppose any change in their state. Here mass is the inertial property analogous to self inductance.
 

Emf = - N(∆magnetic flux)/∆t
N=100turns
∆magnetic flux= -30×10-6Wb
∆t = 0.04sec
Emf = -(100turns)(-30×10-6)/(0.04sec)
Emf = 0.075V