MCQOPTIONS
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MCQOPTIONS
This section includes 43 Mcqs, each offering curated multiple-choice questions to sharpen your Alternating Current and Voltage knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
For most magnetic materials, electron _________ is the main contributor to magnetism. |
| A. | electron orbital motion |
| B. | electron spin |
| C. | proton orbital motion |
| D. | proton spin |
| Answer» C. proton orbital motion | |
| 2. |
An iron nail is more strongly attracted to the |
| A. | south pole of a magnet. |
| B. | north pole of a magnet. |
| C. | None of the above |
| D. | north or south pole-no difference really. |
| Answer» E. | |
| 3. |
Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tackexerts on the magnet is |
| A. | equally huge |
| B. | relatively small. |
| C. | None of the above |
| D. | More information is neede |
| Answer» B. relatively small. | |
| 4. |
Changing the magnetic field intensity in a closed loop of wires induces |
| A. | voltage |
| B. | current. |
| C. | neither of these |
| D. | both of these |
| Answer» E. | |
| 5. |
What causes the temporary magnetism of a common iron nail to go away when the magnetizing force isremoved? |
| A. | it never was a magnet |
| B. | ordinary thermal motion |
| C. | magic |
| D. | vibrations set off by the aligning domains, they can be heard with a amplified stethoscope |
| Answer» C. magic | |
| 6. |
All pieces of iron have magnetic domains, why are most iron nails not magnetic? |
| A. | their domains are all oriented with respect to magnetic poles |
| B. | they cannot conduct electricity |
| C. | their atoms contain 4 electrons that spin magnetism is un-cancelled |
| D. | their domains are randomly oriented, canceling out most magnetic forces |
| Answer» E. | |
| 7. |
Suppose you had a generator that produced an induced voltage of 120 volts. Now suppose that theinternal resistance due to the coil was 10 Ω and the circuit connected had a total resistance of 20 Ω, what wouldan ammeter read in the circuit |
| A. | 4 volts |
| B. | 40 amps |
| C. | 4 amps |
| D. | 12 amps |
| Answer» D. 12 amps | |
| 8. |
The charges moving perpendicular to B experience |
| A. | Minimum force |
| B. | Maximum force |
| C. | Moderate force |
| D. | No force |
| Answer» E. | |
| 9. |
The force on an electron moving in a magnetic field will be the largest when its direction is |
| A. | exactly opposite to the magnetic field direction. |
| B. | the same as the magnetic field direction. |
| C. | at an angle other than 90° to the magnetic field direction |
| D. | perpendicular to the magnetic field direction. |
| Answer» E. | |
| 10. |
When there is a change in the magnetic field in a closed loop of wire, |
| A. | current is made to flow in the loop of wire. |
| B. | a voltage is induced in the wire. |
| C. | all of these |
| D. | electromagnetic induction occurs. |
| Answer» D. electromagnetic induction occurs. | |
| 11. |
A 5 meter wire carrying a current of 2A is at right angles to the uniform magnetic field of 0.5 weber/m2. The force on the wire is |
| A. | 4 N |
| B. | 2 N |
| C. | 1.5 N |
| D. | 5 N |
| Answer» D. 5 N | |
| 12. |
Neon signs require about 12,000 V to operate. If the circuit uses a 120-V power source, the ratio ofprimary to secondary turns on the transformer should be |
| A. | 4.16736111111111 |
| B. | 0.111111111111111 |
| C. | neither of these |
| D. | 0.736111111111111 |
| Answer» E. | |
| 13. |
What happens to the magnetic field intensity if the current carrying wire has three times as many loops,and the same amount of current? |
| A. | it is nine times stronger |
| B. | it is 1/3 as strong |
| C. | it doesn’t change |
| D. | it is three times stronger |
| Answer» E. | |
| 14. |
If a galvanometer is calibrated to measure current, what is it called? |
| A. | current-meter |
| B. | voltmeter |
| C. | ammeter |
| D. | ampmeter |
| Answer» D. ampmeter | |
| 15. |
Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom ofthe lowermost paper clip is a |
| A. | south pole |
| B. | north pole. |
| C. | None of the above |
| D. | north or south pole-no difference really. |
| Answer» C. None of the above | |
| 16. |
The intensity of cosmic rays bombarding the earth\'s surface is largest at the |
| A. | mid-latitudes |
| B. | poles. |
| C. | None of the above |
| D. | equator |
| Answer» C. None of the above | |
| 17. |
Voltage produced by a generator alternates because |
| A. | the changing magnetic field that produces it alternates. |
| B. | unlike a battery, it produces alternating current. |
| C. | in effect it is an ac motor in reverse. |
| D. | alterations in the mechanical energy input. |
| Answer» B. unlike a battery, it produces alternating current. | |
| 18. |
Who was the scientist who first made artificial magnets by rubbing pieces of iron against magnetic rocks? |
| A. | John Mitchell |
| B. | William Gilbert |
| C. | Andre-Marie Ampere |
| D. | Hans Christian Oersted |
| Answer» C. Andre-Marie Ampere | |
| 19. |
Total number of lines of magnetic induction passing through any surface placed perpendicular to the field is called |
| A. | Magnetic induction |
| B. | Flux density |
| C. | Self inductance |
| D. | Magnetic flux |
| Answer» E. | |
| 20. |
A transformer actually transforms |
| A. | magnetic field lines. |
| B. | voltage. |
| C. | non-safe forms of energy to safe forms of energy. |
| D. | generators into motors |
| Answer» C. non-safe forms of energy to safe forms of energy. | |
| 21. |
The metal detectors that people walk through at airports operate via |
| A. | Faraday's law. |
| B. | Ohm's law. |
| C. | Newton's laws. |
| D. | Coulomb's law. |
| Answer» B. Ohm's law. | |
| 22. |
The space around a magnet contains what? |
| A. | mostly nitrogen, with some oxygen and other various gasses |
| B. | a magnetic field |
| C. | an electric field |
| D. | nothing |
| Answer» C. an electric field | |
| 23. |
When looking at iron filings that have been allowed to interact with a magnetic field, what does thedensity of lines suggest? |
| A. | that the magnetic field is weakest there |
| B. | nothing |
| C. | that the electric field is un-canceled there |
| D. | that the magnetic field is strongest there |
| Answer» E. | |
| 24. |
What condition is necessary for an electric charge to have a magnetic field around it? |
| A. | it must be isolated from the opposite charge |
| B. | it must be in a copper wire |
| C. | it must be motionless |
| D. | it must be moving |
| Answer» E. | |
| 25. |
Which electromagnetic device contains an armature ? |
| A. | A speaker |
| B. | A dc generator |
| C. | A relay |
| D. | A solenoid |
| Answer» C. A relay | |
| 26. |
Which electromagnetic device has a movable iron core called a plunger ? |
| A. | A speaker |
| B. | A dc generator |
| C. | A relay |
| D. | A solenoid |
| Answer» E. | |
| 27. |
What is the reluctance of a material that has a length of 0.045 m, a cross-sectional area of 0.015 m 2 , and a permeability of 2500 µWb/At·m? |
| A. | 833.33 µAt/Wb |
| B. | 0.27 At/Wb |
| C. | 1200 At/Wb |
| D. | More information is needed in order to find the reluctance. |
| Answer» D. More information is needed in order to find the reluctance. | |
| 28. |
Which electromagnetic device has a flexible cone ? |
| A. | A speaker |
| B. | A dc generator |
| C. | A relay |
| D. | A solenoid |
| Answer» B. A dc generator | |
| 29. |
How much flux is there in a magnetic field when its flux density is 5000 T and its cross-sectional area is 300 mm 2 ? |
| A. | 16.67 mWb |
| B. | 5.0 Wb |
| C. | 3.0 mWb |
| D. | 1.5 Wb |
| Answer» E. | |
| 30. |
What is the flux density of a magnetic field whose flux is 3000 µWb and cross-sectional area is 0.25 m 2 ? |
| A. | 12,000 T |
| B. | 83,330 T |
| C. | 0 T |
| D. | More information is needed in order to find flux density. |
| Answer» B. 83,330 T | |
| 31. |
Which electromagnetic device uses brushes and a commutator ? |
| A. | A speaker |
| B. | A dc generator |
| C. | A relay |
| D. | A solenoid |
| Answer» C. A relay | |
| 32. |
What is the magnetomotive force (mmf) of a wire with 8 turns carrying three amperes of current? |
| A. | 2,400 At |
| B. | 240 At |
| C. | 24 At |
| D. | 2.4 At |
| Answer» D. 2.4 At | |
| 33. |
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 |
| Answer» B. a permanent magnetic field | |
| 34. |
The induced voltage across a stationary conductor in a stationary magnetic field is |
| A. | zero |
| B. | reversed in polarity |
| C. | increased |
| D. | decreased |
| Answer» B. reversed in polarity | |
| 35. |
The voltage induced across a certain coil is 200 mV. A 120 resistor is connected to the coil terminals. The induced current is |
| A. | 1.7 mA |
| B. | 16 mA |
| C. | 12 mA |
| D. | 120 mA |
| Answer» B. 16 mA | |
| 36. |
The ability of a material to remain magnetized after removal of the magnetizing force is known as |
| A. | permeability |
| B. | reluctance |
| C. | hysteresis |
| D. | retentivity |
| Answer» E. | |
| 37. |
When the north poles of two bar magnets are brought close together, there will be |
| A. | no force |
| B. | a downward force |
| C. | a force of attraction |
| D. | a force of repulsion |
| Answer» E. | |
| 38. |
The unit for permeability is |
| A. | Wb/At × m |
| B. | At/m |
| C. | At/Wb |
| D. | Wb |
| Answer» B. At/m | |
| 39. |
What is the magnetomotive force in a 75-turn coil of wire when there are 4 A of current through it? |
| A. | 18.75 At |
| B. | 30 At |
| C. | 300 At |
| D. | 187 At |
| Answer» D. 187 At | |
| 40. |
What is the flux density in a magnetic field in which the flux in 0.1 m 2 is 600 Wb? |
| A. | 6,000 T |
| B. | 600 T |
| C. | 600 T |
| D. | 6 T |
| Answer» B. 600 T | |
| 41. |
A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will |
| A. | increase |
| B. | decrease |
| C. | remain constant |
| D. | be excessive |
| Answer» C. remain constant | |
| 42. |
What is the flux density when the flux is 5.5 Wb and the cross-sectional area is 6 × 10 –3 m 2 ? |
| A. | 91.7 T |
| B. | 917 T |
| C. | 91 T |
| D. | 9.7 T |
| Answer» C. 91 T | |
| 43. |
What is the reluctance of a material that has a length of 0.07 m, a cross-sectional area of 0.014 m 2 , and a permeability of 4,500 Wb/At × m? |
| A. | 1111 At/Wb |
| B. | 111 At/Wb |
| C. | 11 At/Wb |
| D. | 1 At/Wb |
| Answer» B. 111 At/Wb | |