M6 Topic 3 Part 1 - Electromagnetic Induction

Question 1

what is the magnetic flux density

Answer 1

Φ = BA cosθ

Question 2

what does each symbol mean in the magnetic flux density equation and what units are they measured in

Answer 2

Φ = Magnetic flux denssity (webber (Wb))
B = strength of the magnetic field (tesla(T))
A = Area (m²)
θ = its the reciprocal angle (the thing larry said in that one lesson)

Question 3

What does Faraday’s law state

Answer 3

a change in flux will give way to a emf, which will induce a current

Question 4

what is the faraday’s law equation

Answer 4

ε = -N (ΔΦ)/(Δt)

Question 5

what does each symbol mean in the faraday’s law equation and what units are they measured in

Answer 5

ε = emf induced (volts(V))
N = the number of turns in a coil
Φ = change in magnetic flux (Webber (Wb))
t = change in time (s)

Question 6

what does lenz’s law state

Answer 6

an induced emf will always give rise to a current whose magnetic field opposes the original change in flux

Question 7

what are transformers

Answer 7

devices used to change potential differences of an AC power supply

Question 8

what types of transformers are there (2)

Answer 8

• step up : increase voltage, to transfer over long distances
• step down: decrease voltage (to power domestic devices)

Question 9

what are the components of a transformer

Answer 9

• primary coil
• secondary coil
• soft iron core (laminated sheets)

Question 10

How does a transformer work (5)

Answer 10

1. an alternating current (AC) goes through the primary coil
2. creates a changing magnetic field
3. Change in flux within the laminated soft iron core
4. induces an emf within the secondary coil
5. induces current

Question 11

what are the transformer equations (2)

Answer 11

1. Vₚ/Vₛ = nₚ/nₛ

2. VₚIₚ = VₛIₛ

Question 12

what does each symbol in the transformer equations mean and what units are they measured in (2)

Answer 12

1. voltage per number of coils
Vₚ = voltage of the primary coil (V)
Vₛ = voltage of the secondary coil (V)
nₚ = number of coils in the primary coil
nₛ = number of coils in the secondary coil

2. voltage vs current
Vₚ = voltage of the primary coil (V)
Vₛ = voltage of the secondary coil (V)
Iₚ = current of the primary coil (A)
Iₛ = current of the secondary coil (A)

Question 13

where do transformer lose energy

Answer 13

• Heat loss form eddy currents created in the the soft iron core
• Heat loss from resistance in wire
• Flux loss in the air

Question 14

how is Heat loss form eddy currents in the soft iron core minimised

Answer 14

• separating the core into thin sheets and laminating each layer, makes eddy currents smaller

Question 15

how is Heat loss from resistance in wire minimised (2)

Answer 15

• increase the size of the wire

- change the material the wire is made from to something with less resistance

Question 16

how is Flux loss in the air minimised

Answer 16

• changing to a shell type transformer (coils on the inside of the core)