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PHY 114 > Chpt 8 Electromagnetic Induction > Flashcards

Chpt 8 Electromagnetic Induction Flashcards

1
Q

QUESTION

A

OPTION 1

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2
Q
  1. What is Faraday’s law of electromagnetic induction? (a) The induced e.m.f. in a circuit is proportional to the steady magnetic flux, (b) The induced e.m.f. in a circuit is equal to the negative rate of change of flux through the circuit, (c) Magnetic fields produce electric currents in stationary circuits, (d) Induced e.m.f. opposes the change in current in the circuit
A

Answer: b

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3
Q
  1. In Faraday’s experiment, what was the key observation when a bar magnet was moved into a coil? (a) The galvanometer remained steady, (b) The galvanometer deflected when there was relative motion, (c) The induced current did not depend on the movement of the magnet, (d) Current was induced only when the magnet was stationary
A

Answer: b

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4
Q
  1. According to Lenz’s law, the direction of the induced current is such that it… (a) Reinforces the change in flux, (b) Opposes the change in magnetic flux, (c) Remains constant irrespective of flux, (d) Follows the direction of the applied magnetic field
A

Answer: b

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5
Q
  1. In the equation , what does represent? (a) Magnetic flux, (b) Number of turns in the coil, (c) Electric current, (d) Magnetic field strength
A

Answer: b

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6
Q
  1. What is the induced e.m.f. if a 600-turn coil reduces its magnetic flux from to in 0.015 s? (a) 200 V, (b) 100 V, (c) 20 V, (d) 10 V
A

Answer: c

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7
Q
  1. The magnetic flux through a loop is given by . What is the induced e.m.f. at ? (a) 17.49 V, (b) 14.25 V, (c) 12.48 V, (d) 20.37 V
A

Answer: a

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8
Q
  1. What does the negative sign in Faraday’s law of induction signify? (a) Magnitude of the induced e.m.f., (b) Direction of induced e.m.f. following Lenz’s law, (c) Decrease in magnetic flux, (d) Energy loss in the circuit
A

Answer: b

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9
Q
  1. Which scientist is credited with the discovery of electromagnetic induction? (a) Joseph Henry, (b) James Clerk Maxwell, (c) Michael Faraday, (d) Heinrich Lenz
A

Answer: c

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10
Q
  1. In motional e.m.f., what happens if the conductor moves parallel to the magnetic field? (a) Maximum e.m.f. is induced, (b) No e.m.f. is induced, (c) The e.m.f. depends on the velocity of the conductor, (d) The direction of the e.m.f. reverses
A

Answer: b

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11
Q
  1. What is the relationship between potential difference and motional e.m.f.? (a) , (b) , (c) , (d)
A

Answer: a

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12
Q
  1. What does Lenz’s law ensure in electromagnetic induction? (a) Conservation of charge, (b) Conservation of energy, (c) Conservation of momentum, (d) Conservation of mass
A

Answer: b

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13
Q
  1. What is the induced current in a U-shaped conductor if the resistance is , length is , velocity is , and magnetic field is ? (a) , (b) , (c) , (d)
A

Answer: a

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14
Q
  1. Which of these factors affect the magnetic flux through a loop? (a) Velocity only, (b) Magnetic field only, (c) Area of the loop and angle with the field, (d) Only the number of turns
A

Answer: c

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15
Q
  1. In Figure 8.5(a), what role does the applied force play in the sliding bar experiment? (a) Opposes the induced current, (b) Maintains constant velocity, (c) Increases the resistance of the loop, (d) Reduces the area of the circuit
A

Answer: b

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16
Q
  1. What happens to the polarity of the induced e.m.f. if the direction of motion is reversed? (a) Polarity remains unchanged, (b) Polarity reverses, (c) Induced e.m.f. becomes zero, (d) Current doubles
A

Answer: b

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17
Q
  1. What unit is used to measure magnetic flux? (a) Tesla, (b) Weber, (c) Henry, (d) Volt
A

Answer: b

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18
Q
  1. How is motional e.m.f. calculated in a closed circuit? (a) , (b) , (c) , (d)
A

Answer: b

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19
Q
  1. What does represent in the equation ? (a) Magnetic force, (b) Electric flux, (c) Magnetic flux, (d) Induced current
A

Answer: c

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20
Q
  1. In the context of Faraday’s experiment, which variable does NOT affect the induced current? (a) Relative motion, (b) Strength of the magnet, (c) Number of turns, (d) Shape of the magnetic field
A

Answer: d

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21
Q
  1. A magnetic field directed into the page causes charges to… (a) Move to the center of the conductor, (b) Separate along the length of the conductor, (c) Flow uniformly throughout the conductor, (d) Accelerate toward the edges of the loop
A

Answer: b

22
Q
  1. How is power delivered in the sliding bar experiment related to induced current? (a) , (b) , (c) , (d)
A

Answer: b

23
Q
  1. Which factor does NOT affect motional e.m.f.? (a) Velocity of motion, (b) Length of the conductor, (c) Resistance of the rails, (d) Magnetic field strength
A

Answer: c

24
Q
  1. What happens to the induced current when the resistance of the loop increases? (a) It increases, (b) It decreases, (c) It remains the same, (d) It oscillates
A

Answer: b

25
Q
  1. When does the magnetic flux through a loop remain constant? (a) When there is relative motion between the loop and the field, (b) When the field is steady and the loop is stationary, (c) When the magnetic field is changing, (d) When the area of the loop decreases
A

Answer: b

26
Q
  1. What is the SI unit of resistance? (a) Ampere, (b) Volt, (c) Ohm, (d) Weber
A

Answer: c

27
Q
  1. Faraday’s law of induction states that the induced e.m.f. in a coil is proportional to: (a) The resistance of the coil, (b) The rate of change of magnetic flux, (c) The length of the coil, (d) The area of the coil
A

Answer: b

28
Q
  1. The formula for magnetic flux is: (a), (b), (c), (d)
A

Answer: a

29
Q
  1. According to Lenz’s law, the direction of induced e.m.f.: (a) Aids the change causing it, (b) Opposes the change causing it, (c) Is always clockwise, (d) Depends on the resistance
A

Answer: b

30
Q
  1. Which of the following expressions represents the induced e.m.f. in a moving conductor? (a), (b), (c), (d)
A

Answer: b

31
Q
  1. In a rotating coil, the instantaneous e.m.f. is given by: (a), (b), (c), (d)
A

Answer: c

32
Q
  1. What happens to the e.m.f. in a rotating coil when the magnetic field is perpendicular to the plane of the coil? (a) Maximum, (b) Zero, (c) Increases, (d) Decreases
A

Answer: b

33
Q
  1. In an AC generator, the maximum e.m.f. is given by: (a), (b), (c), (d)
A

Answer: b

34
Q
  1. Transformers operate on the principle of: (a) Electrostatic induction, (b) Electromagnetic induction, (c) Lenz’s law, (d) Coulomb’s law
A

Answer: b

35
Q
  1. The basic transformer equation is: (a), (b), (c), (d)
A

Answer: a

36
Q
  1. A transformer is said to be a step-up transformer if: (a), (b), (c), (d)
A

Answer: b

37
Q
  1. What is the role of slip rings in an AC generator? (a) To step up the voltage, (b) To step down the voltage, (c) To maintain contact between the rotating coil and the external circuit, (d) To generate a uniform magnetic field
A

Answer: c

38
Q
  1. Electric fields induced by changing magnetic fields: (a) Form closed loops, (b) Are conservative, (c) Have static charges, (d) Follow Coulomb’s law
A

Answer: a

39
Q
  1. What device is used to convert mechanical energy into electrical energy? (a) Transformer, (b) Generator, (c) Inductor, (d) Resistor
A

Answer: b

40
Q
  1. In an ideal transformer, if the input power is 100 W, the output power will be: (a) Greater than 100 W, (b) Less than 100 W, (c) 100 W, (d) Depends on efficiency
A

Answer: c

41
Q
  1. Pacemakers make use of: (a) Static electric fields, (b) Induced e.m.f., (c) Transformers, (d) Coulomb forces
A

Answer: b

42
Q
  1. The e.m.f. induced in a loop rotating with angular velocity is proportional to: (a), (b), (c), (d)
A

Answer: b

43
Q
  1. The main advantage of transmitting electricity at high voltages is to: (a) Reduce power loss, (b) Increase current, (c) Reduce transformer efficiency, (d) Increase resistance
A

Answer: a

44
Q
  1. What is the efficiency of a transformer that steps up voltage from 120V to 1200V, with no power loss? (a) 90%, (b) 95%, (c) 99%, (d) 100%
A

Answer: d

45
Q
  1. The sinusoidal nature of e.m.f. in a generator is due to: (a) Constant speed rotation, (b) Non-uniform magnetic flux, (c) Alternating current, (d) Rectified current
A

Answer: a

46
Q
  1. Lenz’s law is a consequence of: (a) Conservation of energy, (b) Coulomb’s law, (c) Ampere’s law, (d) Kirchhoff’s law
A

Answer: a

47
Q
  1. A betatron accelerates electrons using: (a) Coulomb forces, (b) Induced electric fields, (c) Electrostatic forces, (d) Magnetic flux
A

Answer: b

48
Q
  1. Which of these statements is correct for a step-down transformer? (a), (b), (c), (d)
A

Answer: b

49
Q
  1. The condition for maximum e.m.f. in a rotating coil is: (a) Magnetic field is parallel to the coil, (b) Magnetic field is perpendicular to the coil, (c) Rate of change of flux is zero, (d) Rate of change of flux is maximum
A

Answer: d

50
Q
  1. What factor does not affect the e.m.f. induced in a coil? (a) Number of turns, (b) Angular speed, (c) Area of the coil, (d) Coil resistance
A

Answer: d

51
Q
  1. Transformers are not used with: (a) AC circuits, (b) DC circuits, (c) Step-up voltages, (d) Step-down voltages
A

Answer: b

PHY 114 (8 decks)

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