TOP Magnetic Circuit – Electrical Engineering Multiple Choice Questions and Answers
1. 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
2. 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
3. The unit of magnetic flux is
4. Permeability in a magnetic circuit corresponds to______ in an electric circuit.
5. Point out the wrong statement.
Magnetic leakage is undesirable in electric machines because it
(a) lowers their power efficiency
(b) increases their cost of manufacture
(c) leads to their increased weight
(d) produces fringing
6. Relative permeability of vacuum is
(b) 1 H/m
(d) 4n x 10-‘ H/m
7. Permanent magnets are normally made of
(a) alnico alloys
(c) cast iron
(d) wrought iron
8. Energy stored by a coil is doubled when its current is increased by percent.
9. Those magnetic materials are best suited for making armature and transformer cores which have____permeability and_______hystersis loss.
(a) high, high
(b) low, high
(c) high, low
(d) low, low
10. 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