Electromagnetism questions

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Electromagnetism question collection

Review Electromagnetism questions for Physics, with correct answers shown and coverage across magnetic fields; electromagnets; motor and generator effects.

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Question 1

Which ratio describes an ideal transformer?
  1. \(\frac{V_p}{V_s} = \frac{N_p}{N_s}\)
  2. \(\frac{V_p}{V_s} = \frac{N_s}{N_p}\)
  3. \(V_p V_s = N_p N_s\)
  4. \(V_p = V_s\)

Question 2

What gives the direction of the field around a current-carrying wire?
  1. Right-hand rule
  2. Left-hand rule
  3. Faraday's law
  4. Ohm's law

Question 3

What happens to an induced magnet when the field is removed?
  1. It loses most of its magnetism
  2. It keeps all of its magnetism
  3. Its north and south poles exchange places
  4. It becomes electrically charged

Question 4

What happens to the force on a current-carrying wire if the magnetic field strength doubles?
  1. It doubles
  2. It halves
  3. It stays the same
  4. It becomes zero

Question 5

In Fleming's left-hand rule, what direction does the thumb show?
  1. Force
  2. Current
  3. Magnetic field
  4. Induced current

Question 6

A magnet is moved into a coil. What happens to the induced current if its motion is reversed?
  1. It reverses
  2. It doubles
  3. It stays unchanged
  4. It becomes direct current

Question 7

What happens to the induced voltage when a magnet moves faster through a coil?
  1. It increases
  2. It decreases
  3. It stays the same
  4. It falls to zero

Question 8

Which part lets a generator produce direct current instead of alternating current?
  1. A split-ring commutator
  2. A pair of slip rings
  3. A soft iron core
  4. A step-up transformer

Question 9

What is the force on a current-carrying wire in a field called?
  1. Motor effect
  2. Generator effect
  3. Electrostatic induction
  4. Electromagnetic induction

Question 10

Which equation gives the force on a current-carrying wire?
  1. \(F = BIl\)
  2. \(F = B + I + l\)
  3. \(F = \frac{BI}{l}\)
  4. \(F = BI^2\)

Question 11

A coil \(0.3\,\mathrm{m}\) long carries \(2\,\mathrm{A}\) in a \(0.2\,\mathrm{T}\) field. What is the force?
  1. \(0.12\,\mathrm{N}\)
  2. \(0.03\,\mathrm{N}\)
  3. \(1.2\,\mathrm{N}\)
  4. \(0.6\,\mathrm{N}\)

Question 12

What does a transformer do to alternating voltage?
  1. Changes alternating potential difference using a turns ratio
  2. Converts alternating current into direct current
  3. Stores electrical charge between two plates
  4. Changes resistance when its temperature changes

Question 13

For the same power, what happens to the secondary current in a step-up transformer?
  1. It decreases
  2. It increases
  3. It falls to zero
  4. It stays the same

Question 14

What can an electromagnet do that a permanent magnet cannot?
  1. Be switched off
  2. Attract magnetic materials
  3. Produce a magnetic field
  4. Have a north and a south pole

Question 15

Magnetic field lines show direction from where to where?
  1. North to south outside the magnet
  2. South to north outside the magnet
  3. North to south both inside and outside
  4. From the centre towards both poles

Question 16

Which pattern of field is produced by a current through a straight wire?
  1. Concentric circles around the wire
  2. Radial lines pointing outwards
  3. A spiral into the wire
  4. Parallel straight lines

Question 17

What does a moving-coil microphone produce from sound pressure variations?
  1. Variations in electric current
  2. A constant electric current
  3. A permanent magnetic field
  4. A steady mechanical force

Question 18

Which current produces a steady magnetic field in a solenoid?
  1. Direct current
  2. Alternating current
  3. Pulsed light
  4. Static charge

Question 19

What does a loudspeaker produce from variations in electric current?
  1. Variations in sound pressure
  2. A constant sound pressure
  3. A permanent electric charge
  4. A steady magnetic field

Question 20

Which quantity is measured in tesla?
  1. Magnetic field strength
  2. Electric potential
  3. Resistance
  4. Power

Question 21

What happens to an alternator's induced potential difference every half turn?
  1. It reverses
  2. It reaches zero
  3. It increases
  4. It stays constant

Question 22

Which supply is needed for a transformer to operate continuously?
  1. Alternating current
  2. Direct current
  3. Static charge
  4. Pulsed light

Question 23

Which device shows the direction of a magnetic field at one point?
  1. A plotting compass
  2. Iron filings
  3. A steel paperclip
  4. A voltmeter

Question 24

A transformer has more turns on the secondary. What type is it?
  1. Step-up transformer
  2. Step-down transformer
  3. Rectifier
  4. Thermistor

Question 25

What is the role of the split-ring commutator in a DC motor?
  1. It reverses the current every half-turn
  2. It increases the supply potential difference
  3. It removes the magnetic field
  4. It measures the motor’s resistance

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Review Electromagnetism questions for Physics, with correct answers shown and coverage across magnetic fields; electromagnets; motor and generator effects.

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