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Quiz Chapter 4: Electromagnetism

10 questions · Form 5 Physics Bab 4: Electromagnetism

Question 1 of 10Score: 0

Which factor causes energy loss due to hysteresis in a transformer?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Which factor causes energy loss due to hysteresis in a transformer?

  1. Resistance of secondary winding copper wire
  2. Repeated magnetisation and demagnetisation of the core material
  3. Induced circulation currents within the solid core body
  4. Leakage of magnetic flux into surrounding air
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Answer: B

Hysteresis loss occurs because work is done during each a.c. cycle to continuously realign magnetic domains inside the core material.

2. What structural component distinguishes an alternating current (a.c.) generator from a direct current (d.c.) generator?

  1. Rectangular coil
  2. Permanent field magnets
  3. Slip rings
  4. Carbon brushes
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Answer: C

An a.c. generator uses continuous slip rings, whereas a d.c. generator uses a split-ring commutator.

3. Which rule determines the direction of induced current in a straight conductor moving perpendicular to a magnetic field?

  1. Fleming's Right-Hand Rule
  2. Fleming's Left-Hand Rule
  3. Right-Hand Grip Rule
  4. Maxwell's Screw Rule
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Answer: A

Fleming's Right-Hand Rule (generator rule) gives the induced current direction when motion/force and magnetic field are known.

4. Faraday's Law of Electromagnetic Induction states that the magnitude of induced e.m.f. is directly proportional to the:

  1. Resistance of the conductor coil
  2. Rate of cutting or rate of change of magnetic flux linkage
  3. Temperature of the magnetic core
  4. Total length of connecting copper lead wires
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Answer: B

Faraday's Law explicitly relates magnitude of induced e.m.f. to the rate of change of magnetic flux linkage.

5. A bar magnet is pushed rapidly into a solenoid connected to a center-zero galvanometer. What phenomenon causes the galvanometer pointer to deflect?

  1. Thermionic emission
  2. Electromagnetic induction
  3. Electrostatic attraction
  4. Self-heating effect
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Answer: B

Moving a magnet relative to a solenoid causes magnetic flux linkage to change, inducing an e.m.f. via electromagnetic induction.

6. Why can transformers NOT operate when connected to a continuous steady Direct Current (d.c.) supply?

  1. Direct current has too high internal resistance
  2. Direct current creates a constant magnetic field, causing zero rate of change of flux linkage
  3. Direct current melts the soft iron core
  4. Direct current flows only through the secondary coil
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Answer: B

Mutual induction requires a continuously changing magnetic field. Steady d.c. generates static magnetic flux, so no e.m.f. is induced in the secondary coil.

7. How are power losses due to eddy currents reduced in the soft iron core of a transformer?

  1. Using thick copper wires for the winding coils
  2. Laminating the soft iron core with insulated thin sheets
  3. Replacing the soft iron core with steel
  4. Cooling the transformer in water
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Answer: B

A laminated core consists of thin iron sheets insulated from each other, restricting eddy currents to tiny loops and reducing I²R heat loss.

8. Which rule is used to determine the direction of the magnetic force acting on a current-carrying conductor placed in a magnetic field?

  1. Right-Hand Grip Rule
  2. Fleming's Left-Hand Rule
  3. Fleming's Right-Hand Rule
  4. Lenz's Law
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Answer: B

Fleming's Left-Hand Rule determines the force/motion on a current-carrying conductor in an external magnetic field (motor effect).

9. A copper rod falls vertically through a uniform horizontal magnetic field. What happens across the ends of the rod?

  1. An electric potential difference is induced across its ends
  2. The magnetic field vanishes instantly
  3. The copper rod loses its gravitational mass
  4. A steady direct current flows in a closed circle within the rod
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Answer: A

As the moving conductor cuts horizontal magnetic flux lines, an electromotive force (e.m.f.) / potential difference is induced between its ends.

10. What is the primary function of a split-ring commutator in a direct current (d.c.) motor?

  1. To increase the speed of rotation of the coil
  2. To reverse the direction of current in the coil every half-revolution
  3. To switch off the circuit automatically when overloaded
  4. To reduce friction during high-speed rotation
Show answer

Answer: B

The split-ring commutator reverses current flow through the coil every 180° so the turning force remains in the same rotational direction.

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