WorksheetsMAGNETIC CIRCUITS
Total questions: 10
Worksheet time: 5mins
An air gap is usually inserted in magnetic circuits to
A)Increase m.m.f
B)Increase the flux
C)Prevent saturation
D)None of the above
The relative permeability of a ferromagnetic material is
A)Less than one
B)More than one
C)More than 10
D)More than 100 or 1000
The unit of magnetic flux is
A)Henry
B)Weber
C)Ampere-turn/Weber
D)Ampere/meter
Permeability of a magnetic circuit corresponds to………. In an electrical circuit
A)Resistance
B)Resistivity
C) Conductivity
D)Conductance
Point out the wrong statement.
Magnetic leakage is undesirable inn electric machine because it
A)Lower their power efficiency
B)Increases their cost of manufacture
C)Leads to their increased weight
D)Produces fringing
The magnetising force (H) and magnetic flux density (B) are connected by the relation
A)B = µrH/µ0
B)B = µH
C) B = H/µrµ0
D)B = µr/Hµ0
Permanent magnets are normally made of
A)Alnico alloys
B)Aluminium
C)Cast iron
D)Wrought iron
Energy stored by a coil is doubled when its current is increased by ………. percent.
A)25
B)50
C)41.4
D)100
Those magnetic materials are best suited for making armature and transformer cores which have …. permeability and …… hysteresis loss.
A)High, high
B)Low, high
C)High, Low
D)Low, Low
The rate of rise of current through an inductive coil is maximum
A) At 63.2% of its maximum steady value
B)
At the start of the current flow
C)
After one time constant
D)
Near the final maximum value of current
