Magnetism and Electromagnetism problems
- 1. The unit for permeability is
Options- A. Wb/At × m
- B. At/m
- C. At/Wb
- D. Wb Discuss
Correct Answer: Wb/At × m
- 2. The induced voltage across a stationary conductor in a stationary magnetic field is
Options- A. zero
- B. reversed in polarity
- C. increased
- D. decreased Discuss
Correct Answer: zero
- 3. For a given wirewound core, an increase in current through the coil
Options- A. reverses the flux lines
- B. decreases the flux density
- C. increases the flux density
- D. causes no change in flux density Discuss
Correct Answer: increases the flux density
- 4. If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density
Options- A. increases
- B. decreases
- C. remains the same
- D. doubles Discuss
Correct Answer: decreases
- 5. The direction of a magnetic field within a magnet is
Options- A. from south to north
- B. from north to south
- C. back to front
- D. front to back Discuss
Correct Answer: from south to north
- 6. When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage
Options- A. increases
- B. decreases
- C. remains constant
- D. reaches zero Discuss
Correct Answer: increases
- 7. The ability of a material to remain magnetized after removal of the magnetizing force is known as
Options- A. permeability
- B. reluctance
- C. hysteresis
- D. retentivity Discuss
Correct Answer: retentivity
- 8. What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it?
Options- A. 18.75 At
- B. 30 At
- C. 300 At
- D. 187 At Discuss
Correct Answer: 300 At
- 9. When the north poles of two bar magnets are brought close together, there will be
Options- A. no force
- B. a downward force
- C. a force of attraction
- D. a force of repulsion Discuss
Correct Answer: a force of repulsion
- 10. What is the magnetomotive force (mmf) of a wire with 8 turns carrying three amperes of current?
Options- A. 2,400 At
- B. 240 At
- C. 24 At
- D. 2.4 At Discuss
Correct Answer: 24 At
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