Practice Test: Question Set - 04
1. When the current through the coil of an electromagnet reverses, the
- (A) Direction
of the magnetic field reverses
- (B) Direction of
the magnetic field remains unchanged
- (C) Magnetic
field expands
- (D) Magnetic
field collapses
2. A keeper is used to
- (A) Change the direction of magnetic lines
- (B) Amplify flux
- (C) Restore lost flux
- (D) Provide a closed path for flux
3. The unit for permeability is
- (A) Wb/At × m
- (B) At/m
- (C) At/Wb
- (D) Wb
4. What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m?
- (A) 2 AT
- (B) 4 AT
- (C) 6 AT
- (D) 10 AT
5. When a solenoid is activated, the force that moves the plunger is
- (A) An
electromagnetic field
- (B) A permanent
magnetic field
- (C) Varying
voltage
- (D) A steady
current
6. How does the magnetic compass needle behave in a magnetic field?
- (A) It assures a position right angle to
magnetic field
- (B) It starts rotating
- (C) It assures a position which follows a line
of magnetic flux
- (D) None of the above
7. If a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage in the conductor will reverse polarity.
- (A) True
- (B) False
8. For which of the following materials the saturation value is the highest?
- (A) Ferromagnetic materials
- (B) Paramagnetic materials
- (C) Diamagnetic materials
- (D) Ferrites
9. There is 900 mA of current through a wire with 40 turns. What is the reluctance of the circuit if the flux is 400 μWb?
- (A) 14,400 At/Wb
- (B) 1,440 At/Wb
- (C) 9,000 At/Wb
- (D) 90,000 At/Wb
10. Magnetism of a magnet can be destroyed by
- (A) Heating
- (B) Hammering
- (C) By inductive action of another magnet
- (D) By all above methods
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