Induced potential, transformers and the National Grid (physics only) (HT only) common mistakes

Common mistakes

• National Grid transformer reasoning: avoid motors and generators

  Treating motors and generators as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Microphones (HT only), then explain how it links to a student comparing motor and generator effects and the objective to explain how a moving-coil microphone works.

• National Grid transformer reasoning: avoid motors and generators

  Treating motors and generators as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Microphones (HT only), then explain how it links to a calculation using primary and secondary coils and the objective to link movement of a coil in a magnetic field to induced potential difference in a microphone.

• National Grid transformer reasoning: avoid motors and generators

  Treating motors and generators as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Microphones (HT only), then explain how it links to a bar magnet and plotting compass practical and the objective to distinguish microphone generator-effect operation from loudspeaker motor-effect operation.

• National Grid transformer reasoning: avoid primary and secondary...

  Treating primary and secondary coils as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a steel core electromagnet demonstration and the objective to describe a basic transformer as a primary coil and a secondary coil wound on an iron core.

• National Grid transformer reasoning: avoid magnetic field...

  Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a current-carrying wire between magnetic poles and the objective to state that iron is used in the core because it is easily magnetised.

• National Grid transformer reasoning: avoid magnetic field...

  Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a loudspeaker coil moving in a magnetic field and the objective to recognise that knowledge of laminations and eddy currents in the core is not required.

• National Grid transformer reasoning: avoid magnetic field...

  Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to an alternator producing an AC output trace and the objective to explain how an alternating current in one coil induces a current in another coil.

• National Grid transformer reasoning: avoid magnetic field...

  Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a dynamo producing a DC output trace and the objective to explain how the effect of an alternating current in one coil inducing a current in another is used in transformers.

• National Grid transformer reasoning: avoid AC and DC

  Treating AC and DC as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a moving-coil microphone investigation and the objective to state that the ratio of the potential differences across the primary and secondary coils depends on the ratio of the number of turns on each coil.

• National Grid transformer reasoning: avoid magnetic field...

  Treating magnetic field direction and force direction as interchangeable when answering about National Grid transformer reasoning.

  Fix itInstead, identify the exact Unit 4.7 idea in Transformers (HT only), then explain how it links to a step-up transformer on the National Grid and the objective to recall and apply the transformer equation Vp / Vs = np / ns.