3.7.3 Magnetic Fields

Question 1

magnetic flux

Answer 1

BA - for a uniform magnetic field of flux density B that is perpendicular to an area A

Question 2

units of magnetic flux

Answer 2

Weber - Wb

Question 3

magnetic flux density

Answer 3

B - magnetic force per unit length per unit current on a current carrying conductor at right angles to the magnetic field lines

Question 4

units of magnetic flux density

Answer 4

Tesla - T

Question 5

magnetic flux linkage

Answer 5

through a coil of N turns N⍉ = NBAcos⍬ (where B is the magnetic flux density perpendicular to the area A)

Question 6

magnetic force

Answer 6

force on a current carrying wire in a magnetic field F = BILsin⍬/ force on a free-moving particle in a magnetic field F = BQv

Question 7

magnetic flux linkage unit

Answer 7

Weber - Wb

Question 8

uniform magnetic field example

Answer 8

solenoid with a constant current

Question 9

transformer

Answer 9

converts the amplitude of an alternating pd to a different value, consists of: 2 insulated coils, the primary and secondary, wound round soft iron laminated core

Question 10

transformer efficiency

Answer 10

100% efficient transformer has input voltage = output voltage

Question 11

transformer inefficiencies

Answer 11

resistance heating of the current in each coil, heating effect of eddy currents in the core, heating caused by repeated magnetisation and demagnitisation of the core

Question 12

simple electric motor

Answer 12

electric motor with an armature consisting of a single coil of uninsulated wire

Question 13

what could be used to measure the magnetic flux density?

Answer 13

Hall probe