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

Common mistakes

• 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-down transformer for a low-voltage device and the objective to identify Vp and Vs as potential differences in volts.

• 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 student comparing motor and generator effects and the objective to identify np and ns as the number of turns on the primary and secondary coils.

• 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 calculation using primary and secondary coils and the objective to describe a step-up transformer as having secondary potential difference greater than primary potential difference.

• 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 bar magnet and plotting compass practical and the objective to describe a step-down transformer as having secondary potential difference less than primary potential difference.

• 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 steel core electromagnet demonstration and the objective to explain how the ratio of potential differences across the two coils depends on the ratio of turns on each coil.

• 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 current-carrying wire between magnetic poles and the objective to calculate primary potential difference, secondary potential difference, primary turns or secondary turns using transformer ratios.

• 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 state that if transformers were 100 percent efficient, the electrical power output would equal the electrical power input.

• 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 recall and apply the equation Vp x Ip = Vs x Is for a 100 percent efficient transformer.

• 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 identify Vp x Ip as power input and Vs x Is as power output.

• 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 moving-coil microphone investigation and the objective to identify transformer power input and output in watts.