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

Question: Relative permeability of vacuum is__________?

• 1. 1
• 2. 1 H/m
• 3. 1/4JI
• 4. 4n x 10-‘ H/m

Question: Permeability in a magnetic circuit corresponds to________ in an electric circuit.

• 1. resistance
• 2. resistivity
• 3. conductivity
• 4. conductance

Question: The relative permeability of a ferromagnetic material is_____________?

• 1. less than one
• 2. more than one
• 3. more than 10
• 4. more than 100 or 1000

Question: The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following_____________?

• 1. anode drop and cathode drop
• 2. anode drop and arc drop
• 3. cathode drop and arc drop
• 4. anode drop, cathode drop and arc drop

Question: The ionization potential of mercury is approximately_____________?

• 1. 5.4 V
• 2. 8.4 V
• 3. 10.4 V
• 4. 16.4 V