Electromagnetics

Question 1

What is a hysteresis curve?

Answer 1

Graph produced of H (mag field strength) against B (mag flux density) when a magnetic field is applied, removed and re-applied to a magnetic material.

Question 2

What is remanence (Br)?

Answer 2

When the field strength is reduced to 0, the magnetic material is left with some flux called the remanence.

Question 3

What is the coercivity (Hc)?

Answer 3

The value of magnetic field strength (H) required to reduced the flux density to 0

Question 4

What is Faraday’s law?

Answer 4

The emf induced is equal to the rate of change of flux linking the circuit. Current produced opposes mag field of its own (emf produced NOT current)

Question 5

What is Lenz’s law?

Answer 5

Direction of induced EMF is such that any current it produces will oppose the change in flux

Question 6

What is the Lorentz force?

Answer 6

Describes the force acting on a moving charge from both magnetic and electric fields

Question 7

What is self inductance?

Answer 7

Flux also links with conductor that created it- self inductance is the constant of proportionality between self flux linkage and input current

Question 8

What is mutual inductance ?

Answer 8

Constant of proportionality between mutual flux and current

Question 9

What is Ampere’s Law?

Answer 9

The integral of magnetic field strength (H) around a closed path is equal to the current enclosed by that path