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Question: Which rule gives the direction of induced current due to electromagnetic induction? (A) Fleming’s...

Which rule gives the direction of induced current due to electromagnetic induction?
(A) Fleming’s left hand rule
(B) Maxwell’s left hand rule
(C) Ampere’s rule
(D) Fleming right hand rule

Explanation

Solution

Hint : Electromagnetic induction is the Faraday’s law of induction which states that a changing magnetic flux around a conductor will induce emf across the conductor. In a typical generator, this change of flux is caused by a moving (actually rotating) conductor.

Formula used: In this solution we will be using the following formula;
ϕ=BAcosθ\phi = BA\cos \theta where ϕ\phi is the magnetic flux through a loop of wire, BB is the magnetic flux, AA is the area enclosed by the loop and θ\theta is the angle between the area vector and the magnetic field.

Complete step by step answer
According to faraday’s law of induction, an emf is induced across a conductor in which the magnetic flux passing through it is changing. The flux through a loop of conductor is given as ϕ=BAcosθ\phi = BA\cos \theta where BB is the magnetic flux, AA is the area enclosed by the loop and θ\theta is the angle between the area vector and the magnetic field. Hence, there are three ways in which the magnetic flux can vary. One is due to changing magnetic field, another is due to changing area, and another is due to changing angle.
In a generator for an example, the angle is being changed constantly as we rotate the armature.
The Fleming right hand rule, gives the direction of the current while the loop is moving through the magnetic field. It says that, if we make our thumb, index finger and middle finger perpendicular to each other, such that the thumb points in the direction of the motion, the index finger in the direction of the field, then the middle finger will be in the direction of the current.
Hence, the correct answer is D.

Note
For clarity, the current involved when we talk about induced current is the conventional current. Also, the direction of the magnetic field for actual magnets, like in a generator, is the field lines pointing from north to south. And the motion is the instantaneous motion of the particular part of the loop of interest.