GCSE Physics - Generator Effect / Electromagnetic Induction (2026/27 exams)

Main ideas / lesson conveyed

• Generator effect = electromagnetic induction: A potential difference (voltage) is induced when there is relative motion between a magnet and a coil of wire (or a wire loop) that causes a change in magnetic field through the wire.
• Motion must change the magnetic field: If the wire (or magnet) stops moving, the change in magnetic field becomes zero, so the potential difference disappears.
• Direction depends on motion direction: Reversing the relative direction of motion reverses the polarity of the induced potential difference (and therefore reverses the current direction in a closed circuit).
• Need a complete circuit for current: An induced potential difference by itself does not create current unless the ends of the wire are connected to form a closed loop.
• Induction can also fail if there’s no changing field: Moving the wire back and forth may not induce a change in magnetic field (if the magnetic field experienced by the wire isn’t changing), so no induced potential difference/current occurs.
• Magnitudes can be increased: The size of the induced voltage/current can be increased by manipulating:
  1. magnetic field strength,
  2. speed of relative motion,
  3. number of turns in the coil.
• Moving a magnet into/out of a coil: Inserting and removing a single magnet from a coil induces a potential difference and current; reversing the magnet’s motion or swapping magnet poles reverses the current direction.

Key methodology / instruction-like points

Creating induced voltage (generator effect)

• Place a coil of wire (a bent wire forming a loop) between magnets such that there is a magnetic field region.
• Move the wire through the magnetic field (or equivalently move the magnets relative to the wire).
• Ensure there is relative motion so the wire experiences a changing magnetic field.
• Stop moving → the induced potential difference goes to zero (no changing magnetic field).

Getting current

• Connect the two ends of the wire to form a closed circuit.
• When the induced potential difference exists, electrons can flow around the circuit → current flows.

Determining direction of induced effects

• If you reverse the direction of relative motion, the polarity of the induced potential difference swaps.
• In a closed circuit, this means the direction of current reverses.
• You can also reverse current direction by swapping the poles of the magnets (turning the magnet around).

Increasing the size of the induced voltage/current

• Use stronger magnets (stronger magnetic field → larger induced potential difference).
• Move faster (faster relative motion → magnetic field changes more quickly → larger induced potential difference).
• Use more coil turns (more loops/turns → larger induced potential difference).

Single-magnet into/out of a coil (application)

• Move a single magnet into and out of a coil.
• This relative motion changes the magnetic field through the coil → induces a potential difference.
• With a complete circuit, this produces current.
• Reverse magnet motion or swap magnet poles → reverses current direction.

Speakers / sources featured

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