6.6 Changing Magnetic Flux

Question 1

Is magnetic flux density a vector or a scalar?

Answer 1

vector

Question 2

What is the magnetic flux density ?

Answer 2

The force exerted on a 1A carrying wire. Essentially the strength of the magnetic field.

Question 3

What should we think of as magnetic flux density in this subtopic?

Answer 3

How close together the field lines of the magnetic field are.

Question 4

What is a magnetic flux?

Answer 4

A measurement of total magnetic field which passes through an area at 90 degrees.

Question 5

What is magnetic flux measured in?

Answer 5

webers - Wb

Question 6

What is the equation for magnetic flux?

Answer 6

Φ = BA

Question 7

What do these symbols represent?

Answer 7

Φ = magnetic flux 
B = magnetic flux density 
A = area

Question 8

Why knowing the rate of change of magnetic flux is important?

Answer 8

Using the units we can work out that they equal to V, suggesting that emf is produced when magnetic flux changes. This idea is used in electromagnetic induction.

Question 9

What happens when magnetic flux interacts with a electrical conductor by motion?

Answer 9

If a wire cuts through a magnetic flux then an emf is produced as magnetic flux is changed.

Question 10

Show how the units of Φ/t change to give 1V?

Answer 10

Wbs^-1 —> Tm^2s^-1 —> NA^-1m^-1m^2s^-1 —–> NmA^-1s^-1 —–> JC^-1 —–> V

Question 11

What is the magnetic flux linkage?

Answer 11

Flux (magnetic field) through each turn multiplied by the number of turns. Total magnetic flux passing a coil of wire at 90 degrees.

Question 12

Why does something like magnetic flux linkage exist? - magnetic flux

Answer 12

Since each coil seperately receives equal certain amount of magnetic flux.

Question 13

Why does something like magnetic flux linkage exist? - emf

Answer 13

SInce each coil has emf induced in it seperately

Question 14

In this topic what do we use magnetic flux and magnetic flux linkage for ?

Answer 14

To describe the effects of magnetic force on an area.

Question 15

What do we have to do if an area isn’t at 90 degrees to the magnetic field?

Answer 15

We have to use trigonometry e.g. Φ = BAcosx to ensure the two are perpendicular before starting working out.

Question 16

What is the equation for magnetic flux linkage? What do the symbols represent?

Answer 16

Φ = NBA 
N = number of coils 
B = magnetic flux density 
A = area 
Φ = magnetic flux linkage

Question 17

What can the units of magnetic flux linkage be?

Answer 17

Wb or Wb turns

Question 18

What is the difference between magnetic flux and magnetic flux linkage?

Answer 18

They’re both the total measurement of magnetic field that passes through an area a 90 degrees. However linkage is for coils of wire, and a seperate but each coil is linked with certain amount of magnetic flux.