21. The B/H characteristics can be determined using _______
A. Ammeter
B. Fluxmeter
C. Voltmeter
D. Multimeter
Answer: B
The fluxmeter is an electronic display instrument used to measure the magnetic flux of permanent magnets hence it can be used to determine B/H characteristics.
22. The B/H curve can be used to determine?
A. Iron loss
B. Hysteresis loss
C. Voltage loss
D. Eddy’s current loss
Answer: B
Hysteresis loss is a heat loss due to the reversal of magnetization of the transformer core whenever it is subjected to a changing magnetic field. It can be determined using the B/H curve.
23. The B/H ratio is not constant for ________
A. Diamagnetic materials
B. Ferromagnetic materials
C. Paramagnetic materials
D. Non-magnetic materials
Answer: B
As the magnetizing field increases, the relative permeability increases reaches a maximum and then decreases. Due to varying permeability, the B/H ratio is not constant for ferromagnetic materials.
24. When using a fluxmeter, if the flux changes from Φ to -Φ, what happens to the current?
A. Becomes zero
B. Becomes infinity
C. Remains the same
D. Reverses
Answer: D
When the flux changes from Φ to -Φ, the current direction will change as the direction of flux is changing.
25. Why is the coil of a ballistic galvanometer wound on a non-metallic former?
A. To minimize damping when high resistance is connected in series
B. To maximize damping when high resistance is connected in series
C. To minimize damping when high resistance is connected in parallel
D. To maximize damping when high resistance is connected in parallel
Answer: A
The coil of ma ballistic galvanometer is wound on a nonmagnetic former in order to minimize damping when high resistance is connected in series.
26. The ballistic galvanometer is usually lightly damped so that ________
A. It can oscillate
B. It will remain stable
C. Amplitude of the first swing is very large
D. Amplitude of the first swing is very small
Answer: C
The ballistic galvanometer is usually lightly damped so that the amplitude of its first swing is very large.
27. PMMC instruments can be used as a flux meter by _______
A. Using a low resistance shunt
B. Removing the control spring
C. Making the control springs have a large moment of inertia
D. Using a high resistance in series
Answer: B
A PMMC or a permanent moving magnet coil instrument can be used as a fluxmeter by removing the control spring.
28. Hysteresis loss is determined from _______
A. B/H curve
B. H/B curve
C. BH curve
D. B2H curve
Answer: C
Hysteresis loss is basically a heat loss due to the reversal of magnetization of the transformer core whenever it is subjected to a changing magnetic field. It can be determined using the B/H curve.
29. What is a PMMC instrument?
A. Permanent moving magnet coil instrument
B. Permanent machine magnet coil instrument
C. Permanent moving machine coil instrument
D. Premature moving magnet coil instrument
Answer: A
A PMMC instrument is a permanent moving magnet coil instrument. It uses two magnets to create a stationary magnetic field.
30. B/H curve shows the relationship between?
A. Magnetic field strength and magnetic flux
B. Magnetic field strength and magnetic flux density
C. Current and magnetic flux density
D. Voltage and magnetic flux density
Answer: B
The B/H curve shows the relation between magnetic field strength and magnetic flux density.
