  Patterns of problems

## Electromagnetic Induction

1
Pattern: Determining induced EMF when parameters of a coil/solenoid are varied.
Description: The induced emf in a coil can be varied by
1. Change in the magnetic field
2. Change in the area of the loop
3. Change in the angle between the field and the loop So the induced EMF is asked when either one or all of the parameters of a coil/loop/solenoid are changed.
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2
Pattern: Determining the direction of induced current/ EMF in a coil, conductor.
Description: Whenever the magnetic flux linked to a coil/ conductor varies with time, an EMF is induced in it. The direction of induced EMF is such that the magnetic field induced by the induced current opposes the change in the external magnetic flux. This is the result of Lenz's Law. We are asked to determine the direction/ polarity of induced EMF / current.
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3
Pattern: Determining motional EMF and the related quantities.
Description: An emf can be induced by moving a conductor instead of varying the magnetic field, that is, by changing the magnetic flux enclosed by the circuit. This is called Motional EMF. Questions based on determining the emf induced, force required to pull the conductor, power required to do so, and heat dissipated are asked.
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4
Pattern: Determining EMF induced in a rigid conductor rotating in a magnetic field.
Description: The conductor doesn't always need to be moving in a linear motion in a magnetic field for EMF to be induced. Rotational motion can also induce emf in it. We are asked to calculate the EMF induced.
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5
Pattern: Determining the mutual inductance for a pair of coils.
Description: When current flowing in one of two nearby coils is charged, the magnetic flux linked with the other coil changes; due to which an emf is induced in it (other coil). This phenomenon of electromagnetic induction is called the mutual induction. We are asked to derive the mutual inductance for this pair of two coils.
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6
Pattern: Working of an AC generator.
Description:The working principle of an AC generator is asked, and then we are asked to derive the expression for its induced EMF.
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