1. One farad equals
A. 1 coulomb/volt
B. 1 newton/coulomb
C. 1 newton-meter
D. 1 volt/second/ampere
2. Which of the following is used by permanent magnets as the magnetic material?
A. iron
B. nickel
C. soft steel
D. hardened steel
3. Which of the following is used by temporary magnets as the magnetic material?
A. Hardened steel
B. Cobalt steel
C. Soft iron
D. Tungsten steel
4. What is the main advantage of temporary magnets?
A. The magnetic flux can be changed.
B. Hysteresis can be decreased.
C. Magnetic materials can be used.
D. Abundance of ferromagnetic material that can be temporarily magnetized.
5. Permanent magnets can be found in
A. electric bells
B. earphones
C. relays
D. dynamic loudspeakers
6. Temporary magnets are commonly employed in
A. electric instruments
B. motors
C. moving coils loudspeakers
D. magnetos
7. The force between two magnetic poles is _______ their pole strengths.
A. directly proportional to
B. the sum of
C. inversely proportional to
D. the product of
8. If the distance between two magnetic poles decreases by 2 times, the force between them
A. decreases two times
B. increases four times
C. increases two times
D. decreases four times
9. The force between two magnetic poles is _____ the relative permeability of the medium.
A. directly proportional to
B. independent of
C. inversely proportional to
D. equal to
10. Two similar poles, each 1Wb, placed 1 m apart in air will experience a repulsive force of
A. 63000 N
B. 63 × 10^-3 N
C. 8 × 10^12 N
D. 796 kN
11. One weber of flux is equal to _______ magnetic lines of force.
A. 10^6
B. 10^10
C. 4π × 10^7
D. 10^8
12. The unit of flux density is
A. Wb/m
B. Tesla
C. At/m
D. N/Wb
13. What is the typical saturation flux density for most magnetic materials?
A. 4 Wb/m^2
B. 5 Wb/m^2
C. 1 Wb/m^2
D. 2 Wb/m^2
14. Magnetic field intensity is a ________ quantity.
A. scalar
B. phasor
C. vector
D. variable
15. The force acting on a pole of 5 Wb is 25 N. What is the intensity of the magnetic field?
A. 5 N/Wb
B. 25 N/Wb
C. 125 N/Wb
D. 0.2 N/Wb
16. The relative permeability of a magnetic material is 10^5. What is its permeability?
A. 4π × 10^5 H/m
B. 4π × 10^-12 H/m
C. 4π × 10^-2 H/m
D. 4π × 10^-7 H/m
17. Which of the following has the highest permeability?
A. Soft iron
B. Steel
C. Air
D. Permalloy
18. A magnetic pole produces 5000 field lines. How much is the flux in webers?
A. 50 × 10^-6
B. 5 × 10^-6
C. 500 × 10^-6
D. 500 × 10^-5
19. As the magnetic intensity decreases, the relative permeability of a magnetic material
A. decreases
B. remains the same
C. increases
D. becomes zero
20. The permeability of a material having a flux density of 5 Wb/m^2 is 10^-5 H/m. What is the value of magnetizing force?
A. 5 × 10^-5 N/Wb
B. 500 × 10^3 N/Wb
C. 4π × 10^-7 N/Wb
D. 4π × 10^7 N/Wb
21. When the relative permeability of a material is slightly less than 1, it is called _____ material.
A. diamagnetic
B. ferromagnetic
C. paramagnetic
D. non-magnetic
22. When the relative permeability of a material is slightly more than 1, it is called ______ material.
A. diamagnetic
B. ferromagnetic
C. paramagnetic
D. non-magnetic
23. Which of the following is a diamagnetic material?
A. Aluminum
B. Silver
C. Air
D. Cobalt
24. Which of the following is a paramagnetic material?
A. Carbon
B. Bismuth
C. Copper
D. Oxygen
25. The greater percentage of materials is _________.
A. diamagnetic
B. paramagnetic
C. ferromagnetic
D. non-magnetic
26. When the relative permeability of a material is much greater than 1, it is called _______ material.
A. diamagnetic
B. ferromagnetic
C. paramagnetic
D. non-magnetic
27. The flux density in an air-cored coil is 10^-3 Wb/m^2. With a cast iron core of relative permeability 100 inserted, the flux density will become
A. 10^-3 Wb/m^2
B. 10^-2 Wb/m^2
C. 10^3 Wb/m^2
D. 0.1 Wb/m^2
28. At/m is a unit of
A. mmf
B. magnetic force
C. reluctance
D. magnetic flux density
29. The direction of force o a current carrying conductor placed in a magnetic field can be found by
A. Cork screw rule
B. Fleming’s left hand rule
C. Fleming’s right hand rule
D. using a compass
30. When a current carrying conductor is placed in a magnetic field, the maximum force will act on the conductor when the conductor is at an angle of _______ to the magnetic field.
A. 45o
B. 60o
C. 30o
D. 90o
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