Which of these could be the output for a dynamo? A. B. C. D. (i) Figure 17 shows the output from a battery. Explain why a transformer will not work with the input current in Figure 17. (ii) A transformer has 30 turns on the primary coil and 150 turns on the secondary coil. Calculate the potential difference across the secondary coil. Use an equation selected from the list of equations at the end of this paper. potential difference = __ V (c) High voltage transmission cables and transformers are used in the national grid. Explain how using high voltage transmission cables and transformers allows the distribution of electrical power around the United Kingdom to be as efficient as possible. Refer to the following equations in your answer. P = P × R V₁ × I₁ = V₂ × I₂

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Which of these could be the output for a dynamo? A - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1

Question 9

Which of these could be the output for a dynamo? A. B. C. D. (i) Figure 17 shows the output from a battery. Explain why a transformer will not work with th... show full transcript

Worked Solution & Example Answer:Which of these could be the output for a dynamo? A - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1

Step 1

Explain why a transformer will not work with the input current in Figure 17.

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Answer

Transformers require an alternating current (AC) to induce a potential difference in the secondary coil through electromagnetic induction. The current shown in Figure 17 is direct current (DC), as indicated by its flat and unidirectional output. DC does not change direction or magnitude, thus no changing magnetic field is produced, rendering the transformer ineffective.

Step 2

Calculate the potential difference across the secondary coil.

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Answer

To find the potential difference ( $V_s$ ) across the secondary coil, we can use the transformer equation:

$\frac{V_s}{V_p} = \frac{N_s}{N_p}$

Where:

$V_p = 25\, V$ (potential difference across the primary coil)
$N_p = 30$ (number of turns on the primary coil)
$N_s = 150$ (number of turns on the secondary coil)

Substituting the known values:

$\frac{V_s}{25} = \frac{150}{30}$

This simplifies to:

$\frac{V_s}{25} = 5$

Rearranging gives:

$V_s = 25 \times 5 = 125\, V$

Step 3

Explain how using high voltage transmission cables and transformers allows the distribution of electrical power around the UK to be as efficient as possible.

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Answer

High voltage transmission cables are implemented to reduce energy loss due to resistance in the wires. By increasing voltage, the current can be decreased for the same power level, since

$P = V \times I$

This means less energy is lost as heat, per the relationship $P = I^2 \times R$ , where $R$ is the resistance of the wires. Additionally, transformers are used to step up the voltage for transmission and step it down for safe consumption. This combination allows power to be distributed more effectively over long distances with minimal losses.

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Which of these could be the output for a dynamo? A - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1

Worked Solution & Example Answer:Which of these could be the output for a dynamo? A - Edexcel - GCSE Physics - Question 9 - 2018 - Paper 1

Explain why a transformer will not work with the input current in Figure 17.

Calculate the potential difference across the secondary coil.

Explain how using high voltage transmission cables and transformers allows the distribution of electrical power around the UK to be as efficient as possible.

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