Question: A ferrite core has less eddy current loss than an iron core because_______________?

• 1. ferrites have high resistance
• 2. ferrites are magnetic
• 3. ferrites have low permeability
• 4. ferrites have high hysteresis

Question: Laminated cores, in electrical machines, are used to reduce____________?

• 1. copper loss
• 2. eddy current loss
• 3. hysteresis loss
• 4. all of the above

Question: While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit ?

• 1. E.m.f.
• 2. Current
• 3. Current density
• 4. Conductivity

Question: The unit of retentivity is____________?

• 1. weber
• 2. weber/sq. m
• 3. ampere turn/meter
• 4. ampere turn

Question: Conductance is analogous to_____________?

• 1. permeance
• 2. reluctance
• 3. flux
• 4. inductance

Question: Hard steel is suitable for making permanent magnets because_____________?

• 1. it has good residual magnetism
• 2. its hysteresis loop has large area
• 3. its mechanical strength is high
• 4. its mechanical strength is low

Question: Those materials are well suited for making permanent magnets which have ________ retentivity and _________ coercivity.

• 1. low, high
• 2. high, high
• 3. high, low
• 4. low, low

Question: Conductivity is analogous to____________?

• 1. retentivity
• 2. resistivity
• 3. permeability
• 4. inductance

Question: When both the inductance and resistance of a coil are doubled the value of________________?

• 1. time constant remains unchanged
• 2. initial rate of rise of current is doubled
• 3. final steady current is doubled
• 4. time constant is halved

Question: Energy stored by a coil is doubled when its current is increased by percent___________?

• 1. 25
• 2. 50
• 3. 41.4
• 4. 100