Lesson 7.5.1

7.5.1 Factors affecting induced e.m.f. Quiz: Pearson Edexcel Physics, Unit 7

20 questions

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Lesson 7.5.1, Factors affecting induced e.m.f.: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 7: Electric and Magnetic Fields, written with Revision Ninja.

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The 20 questions

  1. When a coil moves relative to a permanent magnet, which factor does NOT increase the induced e.m.f.?

    • Using a magnet with a stronger magnetic field
    • Moving the magnet and coil relative to each other more quickly
    • Increasing the number of turns on the coil
    • Moving the coil more slowly past the magnet
  2. The e.m.f. induced in a coil depends on which quantity?

    • The resistance of the coil multiplied by the current through it
    • The rate of change of magnetic flux linkage through the coil
    • The total magnetic flux linkage through the coil at a single instant
    • The mass of the magnet multiplied by the speed of the coil
  3. If the number of turns on a coil is doubled, with the same rate of change of flux through each turn, what happens to the induced e.m.f.?

    • It is unchanged
    • It doubles
    • It halves
    • It quadruples
  4. A coil is moved twice as fast past the same magnet. What happens to the induced e.m.f.?

    • It halves
    • It is unchanged
    • It quadruples
    • It doubles
  5. When the current in one coil changes, what determines the e.m.f. induced in a neighbouring coil linked with it?

    • The steady value of current in the first coil alone, regardless of any change
    • The rate of change of current in the first coil and how much of its flux links the second coil
    • The total charge that has flowed through the first coil since it was switched on
    • The resistance of the second coil only, with no dependence on the first coil
  6. A coil connected to a sensitive meter gives a larger deflection when a magnet is pushed into it more quickly. Which is the correct explanation?

    • A faster movement reduces the number of turns linked with the magnet, which increases the e.m.f.
    • A faster movement increases the total flux through the coil, which is then larger than before
    • A faster movement increases the resistance of the coil, so a larger current flows
    • A faster movement produces a greater rate of change of flux linkage, so a larger e.m.f. is induced
  7. An induced e.m.f. of 2.0 V is produced in a coil. The magnet is replaced by one of twice the field strength, and the coil is moved at half the original speed. What is the new e.m.f.?

    • 1.0 V
    • 2.0 V
    • 8.0 V
    • 4.0 V
  8. A coil of N turns is rotated so that its plane becomes parallel to a uniform magnetic field, instead of perpendicular to it. What happens to the flux linkage through the coil in that orientation?

    • It doubles
    • It reaches a maximum
    • It is unchanged
    • It falls to zero
  9. A coil is pushed at constant speed into a region of uniform magnetic field. Why is an e.m.f. induced only while the coil is entering or leaving the field?

    • The coil is only able to conduct current while it is partly inside the field
    • The field is weakest at the edges of the region and only there does it induce e.m.f.
    • The coil's resistance changes only while it is partly inside the field region
    • The flux linkage changes only while the coil is entering or leaving the field, and is constant while wholly inside it
  10. The number of turns in a secondary coil is increased for the same rate of change of flux. How does the induced e.m.f. change?

    • It increases in direct proportion to the number of turns
    • It increases with the square of the number of turns
    • It decreases in inverse proportion to the number of turns
    • It is unchanged because the flux per turn is the same
  11. A coil has an induced e.m.f. of 12 V. The number of turns is halved and the rate of change of flux per turn is doubled. What is the new e.m.f.?

    • 12 V
    • 6.0 V
    • 24 V
    • 3.0 V
  12. A magnet is passed quickly through a coil. The peak e.m.f. is doubled when the speed is doubled. Compared with the slow pass, how does the total change in flux linkage compare?

    • It is unchanged, because the change of flux linkage from start to end is the same
    • It quadruples, because flux change is proportional to the square of speed
    • It halves, because the faster pass allows less time for the flux to change
    • It doubles, because the change in flux is proportional to speed
  13. A coil of 500 turns and area 0.0010 m^2 is removed from a uniform field of flux density 0.10 T in 0.10 s, with the field perpendicular to the coil at the start. What is the average induced e.m.f.?

    • 0.00050 V
    • 5.0 V
    • 0.050 V
    • 0.50 V
  14. A student says that moving a magnet through a coil at constant speed can never induce an e.m.f. Which response is correct?

    • The student is right: an e.m.f. is only induced when the speed of the coil changes
    • The student is wrong: any change in the flux linkage through the coil, including motion through a field gradient, can induce an e.m.f.
    • The student is right, because the magnet must always be held stationary to induce an e.m.f.
    • The student is wrong because only a coil at rest can ever have an e.m.f. induced in it
  15. A student thinks that induced e.m.f. depends on the magnetic flux itself rather than its rate of change. Which response is correct?

    • The student is wrong: a constant flux linkage induces no e.m.f., since the e.m.f. depends on the rate of change of flux linkage
    • The student is wrong because magnetic flux cannot be linked with a coil at all
    • The student is right, but only when the coil has more than ten turns
    • The student is right: the e.m.f. is proportional to the magnetic flux at any instant
  16. In a pair of coils, which change in the primary coil would produce the largest induced e.m.f. in the secondary coil?

    • A steady primary current with the same flux linked to the secondary coil
    • A reversal of the secondary coil's own resistance with no change in the primary
    • A rapid change in the primary current, with most of the flux linked to the secondary coil
    • A slow change in the primary current with little flux linked to the secondary coil
  17. What is the SI unit of magnetic flux linkage?

    • The volt, V
    • The henry, H
    • The weber, Wb
    • The tesla, T
  18. A 300-turn coil has the flux through each turn fall from 0.004 Wb to zero in 0.020 s. What is the average induced e.m.f.?

    • 60 V
    • 0.24 V
    • 6.0 V
    • 600 V
  19. Which observation best shows that induced e.m.f. depends on relative motion between a coil and a magnet?

    • A magnet held stationary inside a coil induces no reading, but moving the magnet or the coil produces one
    • A coil of many turns produces a reading even when no magnet is nearby
    • A stronger magnet produces a reading even when it is held stationary inside the coil
    • A magnet held stationary near a coil always produces a steady reading on the meter
  20. A coil of area A rotates at constant angular velocity in a uniform magnetic field. When is the induced e.m.f. greatest?

    • When the plane of the coil is parallel to the field, since the flux linkage is then changing fastest
    • When the flux linkage is at its maximum value in the perpendicular position
    • When the plane of the coil is perpendicular to the field, since the flux linkage is then greatest
    • When the coil is momentarily at rest, since the flux linkage is then constant

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