Gap in knowledge - Electromagnetism

Question 1

What is the left hand rule?

Answer 1

Determines direction of magnetism.
- Thumb - CURRENT
- Index - MAG FIELD DIRECTION

Question 2

Does an increase in the length of coil increase or decrease the magnetic strength?

Answer 2

Decrease (more resistance)

Question 3

What is the unit for Magnetic Flux?

Answer 3

Webers

Question 4

What is the unit for Flux Density?

Answer 4

Webers/meter
- OR Tesla (B)

Question 5

What is the unit of magnetic field strength?

Answer 5

Ampere/meter
- H

Question 6

What is the unit for permeability?

Answer 6

Henrys / meter
- u (mu)

Question 7

What do points 1,2 and 3 mean on the B-H curve?

Answer 7

1 - Resistance in domains aligning, so curve is shallow
2 - The domains readily realign, steeper curve
3 - Domains are saturated, any additional magnetizing force only gives a small increase in flux density.

Question 8

What is Coercivity?

Answer 8

The magnetizing force required to reduce REMNANT FLUX DENSITY to zeroW

Question 9

What is Retentivity?

Answer 9

Ability to retain magnetism

Question 10

What is the Hysteresis Loop?

Answer 10

the ‘Lagging behind’ of flux density compared to magnetizing force.
- Determines if material makes good permanent magnet
- Area enclosed in loop = Energy loss (e.g. heat)

Question 11

Does transformers have a small or large enclosed hystersis loop?

Answer 11

Small enclosed loop, to reduce energy loss

Question 12

Do permanent magnets have a small or large enclosed hysterises loop?

Answer 12

Large, wide hysteresis loop.

Question 13

What happens at saturation?

Answer 13

Material behaves like a lower permeability material, which lowers inductance value in coils and inductors.
- An increase in field strength only increases flux density a bit
- Magnetic devices are operated WELL BELOW SATURATION due to lower inductance value.