Unit 5- Electric Fields, Magnetic Fields and Capacitance

Question 1

Electric Field

Answer 1

Force per unit positive charge

Question 2

Magnetic Flux Density

Answer 2

Flux density perpendicular to a wire = magnetic force on a wire / (length of wire x current flowing through wire)

Question 3

Tesla

Answer 3

1 tesla = the flux density that causes a force of 1 newton on a wire of length 1 metre carrying a current of 1 ampere

Question 4

Magnetic Flux

Answer 4

Magnetic flux = magnetic flux density x cross-sectional area perpendicular to field

Question 5

Weber

Answer 5

1 weber = the flux due to a flux density of 1 tesla passing through an area of 1m^2

Question 6

Magnetic Flux Linkage

Answer 6

Flux linkage to a coil = flux passing through one turn x number of turns

Question 7

Faraday’s law of electromagnetic induction

Answer 7

Induced e.m.f. is proportional to the rate of change of magnetic flux linkage

Question 8

Lenz’s Law

Answer 8

An induced e.m.f. will always oppose the change that caused it

Question 9

Capacitance

Answer 9

Charge per unit potential difference

Question 10

Farad

Answer 10

Coulomb per volt

Question 11

Time Constant

Answer 11

Time for the charge on a capacitor to fall by a factor of e