Electromagnetic induction (Unit 4)

Question 1

What is magnetic flux (Φ) and it’s units?

Answer 1

• AB cos theta
• unit - Wb

Question 2

What is flux linkage and it’s units?

Answer 2

• NΦ
• unit- Wb

Question 3

What is Faraday’s law (words)?

Answer 3

-when the flux linking an electrical circuit is changing, an emf is induced in the circuit of magnitude equal to the rate of
change of flux linkage

Question 4

What is Faraday’s law equation?

Answer 4

• Induced EMF (V) = − ΔNϕ/Δt
  ​

Question 5

What is Lenz’s law?

Answer 5

-the direction of any current resulting from an induced emf is
such as to oppose the change in flux linkage that is causing
the current

Question 6

Why is there a negative sign in Faraday’s law?

Answer 6

-due to Lenz’s law

Question 7

How to work out direction of induced current?

Answer 7

-Fleming’s right hand rule

Question 8

What are the two ways of inducing an EMF?

Answer 8

-area changing over time
-flux density changing over time

Question 9

How to work out induced EMF when area changes over time (conducting rod moving)?

Answer 9

Induced EMF (V) = -Blv

Question 10

What factors affected EMF in a coil when rotating?

Answer 10

-flux density
-area of the coil
-angular velocity of the rotation (same change in flux density, smaller time)
-position of coil

Question 11

When theta is 0 what is EMF and flux?

Answer 11

-cosθ = 1
-flux linkage is a
maximum at that point
-rate of change of flux linkage is at its minimum.
-Emf = 0

Question 12

When theta is 90 what is EMF and flux?

Answer 12

-cosθ = 0
-flux linkage is 0 at that point
-the rate of change of
flux linkage is at its maximum
- EMF = max