EM induction

Question 1

What is magnetic flux?

Answer 1

• magnetic flux density, B, is a measure of the strength of a magnetic field
  
  • it helps us to think of it as number of field lines per unit area
• the total magnetic flux, Φ, passing through an area, A, perpendicular to a magnetic field, B, is defined as:
  
  • Φ = BA
  • measured in Wb
  • thought of as toptal number of field lines

Question 2

What happens if there is relative motion between a conducting rod and a magnetic field?

Answer 2

• if there is relative motion between a conducting rod and a magnetic field, theelectrons in the rod will experience a force, which causes them to accumulate at one end of the rod
• this induces an electromotive force across the end of the rod
  
  • this is called EM induction

Question 3

How can an emf being induced in a flat coil or solenoid?

Answer 3

• moving the coil
  
  • towards or away from the poles of a magnet
• moving a magnet
  
  • ​towards or awy from the cvoil

Question 4

In either case, what causes the emf?

Answer 4

• causes by the magnetic flux that passes through the coil changing

Question 5

What happens if the coil is part of complete circuit?

Answer 5

• an induced current will flow through it

Question 6

What does the size of the emf induced depend on when moving a coil in a magnetic field>

Answer 6

• magnetic flux passing through coil, Φ
• number of turns in the coil that cut the flux, N

Question 7

What is flux linkage?

Answer 7

• the product of the number of turns and the magnetic flux passing through the coil
• NΦ = BAN
  
  • for a coil perpendicular to the field

Question 8

What does the rate of change in flux linkage show?

Answer 8

• rate of change of flux linkage tells you how strong the elctromotive force will be in volts
• a change in flux linkage of one weber per second will induce an electromotive force of 1 volt in a loop of wire

Question 9

what do you do if the magnetic flux isn’t perpendicular to the area?

Answer 9

• need to use trig to resolve the magnetic field vector into components that are parallel and perpendicular to the area
• Φ BAN cosθ
  
  • where θ is the angle between the field and the normal to the plane of the loop