Deck 14: Magnetic Circuits

Question 1

A closed path within an electrical machine in which lines of magnetic flux are confined is generically termed a

A) stator'
B) rotor'
C) core'
D) magnetic circuit'

Answer 1

magnetic circuit'

Question 2

A magnetic circuit's magnetomotive force is equivalent to the __________ in an electric circuit

A) voltage gradient
B) voltage
C) resistance
D) current

Answer 2

voltage

Question 3

A magnetic circuit's magnetic flux is equivalent to the __________ in an electric circuit

A) voltage gradient
B) voltage
C) resistance
D) current

Answer 3

current

Question 4

A magnetic circuit's reluctance is equivalent to the __________ in an electric circuit

A) voltage gradient
B) voltage
C) resistance
D) current

Question 5

A magnetic circuit's magnetic field strength is equivalent to the __________ in an electric circuit

A) voltage gradient
B) voltage
C) resistance
D) current

Question 6

The SI unit of measurement for magnetomotive force is the

A) weber
B) ampere per weber
C) ampere
D) ampere per metre

Question 7

The SI unit of measurement for magnetic flux is the

A) weber
B) ampere per weber
C) ampere
D) ampere per metre

Question 8

The SI unit of measurement for reluctance is the

A) weber
B) ampere per weber
C) ampere
D) ampere per metre

Question 9

The SI unit of measurement for magnetic field strength is the

A) weber
B) ampere per weber
C) ampere
D) ampere per metre

Question 10

The relationship between magnetomotive force, magnetic flux, and reluctance is

A) mmf = flux x reluctance
B) mmf = flux/reluctance
C) mmf = reluctance/flux

Question 11

In a magnetic circuit, the equivalent of 'conductivity' is called

A) resistivity'
B) permittivity'
C) permeability'
D) susceptibility'

Question 12

Diamagnetic' materials cause a slight __________ in the flux density within that material, when placed within a uniform magnetic field

A) increase
B) decrease

Question 13

paramagnetic' materials cause a slight __________ in the flux density within that material, when placed within a uniform magnetic field

A) increase
B) decrease

Question 14

An 'homogenous' magnetic circuit is one in which the magnetic flux is formed within

A) entirely the same material
B) different materials
C) ferromagnetic materials
D) non-ferromagnetic materials

Question 15

An 'compound' magnetic circuit is one in which the magnetic flux is formed within

A) entirely the same material
B) different materials
C) ferromagnetic materials
D) non-ferromagnetic materials

Question 16

A motor's magnetic circuit is an example of

A) an homogenous circuit
B) a compound circuit

Question 17

A transformer's core is an example of

A) an homogenous magnetic circuit
B) a compound magnetic circuit

Question 18

A graph which plots the relationship between magnetic field strength and magnetic flux density is called a

A) magnetisation curve'
B) B-H curve'
C) either of the above

Question 19

The upper end of the above curve starts to flatten off, as the sample of magnetic material approaches

A) remenance
B) saturation
C) coercivity
D) hysteresis

Question 20

When the magnetic field strength is reduced towards zero, the resulting change in flux density tends to lag behind, due to a property called

A) remenance
B) saturation
C) coercivity
D) hysteresis

Question 21

When the magnetic field strength reaches zero, the sample of magnetic material retains some flux density, called

A) remenance
B) saturation
C) coercivity
D) hysteresis

Question 22

To completely remove any remaining magnetic flux density from the sample of magnetic material, the magnetic field strength must be reversed to a value termed its

A) remenance
B) saturation
C) coercivity
D) hysteresis

Question 23

The curve resulting from plotting the magnetic flux density against the magnetic field strenght applied over a complete cycle, is termed a

A) magnetisation curve
B) B-H curve
C) hysteresis curve

Question 24

The volume enclosed by the above curve represents the __________ necessary to completely magnetise and demagnetise a sample of magnetic material in both directions

A) effort
B) energy
C) power

Question 25

A small area enclosed by the above curve is typical of __________ magnetic materials, such as __________

A) soft, steel
B) soft, iron
C) hard, steel
D) hard, iron

Question 26

A large area enclosed by the above curve is typical of __________ magnetic materials, such as __________

A) soft, steel
B) soft, iron
C) hard, steel
D) hard, iron