9.1 A generator is shown below. Assume that the coil is in a vertical position. 9.1.1 Is the generator above AC or DC? Give a reason for the answer. 9.1.2 Sketch an induced emf versus time graph for ONE complete rotation of the coil. (The coil starts turning from the vertical position.) 9.2 An AC generator is operating at a maximum emf of 340 V. It is connected across a toaster and a kettle, as shown in the diagram below. The toaster is rated at 800 W, while the kettle is rated at 2 000 W. Both are working under optimal conditions. Calculate the: 9.2.1 rms current passing through the toaster 9.2.2 Total rms current delivered by the generator.

NSC Physical Sciences Electrodynamics: Electrical Machines (Generators and Motors): 9.1 A generator is shown below.

9.1 A generator is shown below - NSC Physical Sciences - Question 9 - 2016 - Paper 1

Question 9

9.1 A generator is shown below. Assume that the coil is in a vertical position. 9.1.1 Is the generator above AC or DC? Give a reason for the answer. 9.1.2 Sketch ... show full transcript

Worked Solution & Example Answer:9.1 A generator is shown below - NSC Physical Sciences - Question 9 - 2016 - Paper 1

Step 1

Is the generator above AC or DC? Give a reason for the answer.

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Answer

The generator is a DC (Direct Current) generator because it uses a split ring or commutator. This component ensures that the current flows in one direction, which is characteristic of DC generators.

Step 2

Sketch an induced emf versus time graph for ONE complete rotation of the coil.

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Answer

The graph would depict a sinusoidal wave, starting from zero voltage when the coil is in a vertical position, reaching maximum positive emf, returning to zero emf as it passes through the horizontal position, reaching maximum negative emf, and finally returning back to zero. This pattern represents the alternating nature of the induced emf over time.

Step 3

Calculate the rms current passing through the toaster.

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Answer

The rms current through the toaster can be calculated using the formula:

$I_{rms} = \frac{P_{toaster}}{V_{rms}}$

Substituting the values: $I_{rms} = \frac{800 \text{ W}}{340 \text{ V}} \approx 2.35 ext{ A}$

Step 4

Calculate the total rms current delivered by the generator.

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Answer

To find the total rms current delivered by the generator, we first calculate the currents through both the toaster and kettle. The rms current through the kettle is given by:

$I_{rms, kettle} = \frac{P_{kettle}}{V_{rms}}$

Substituting the values: $I_{rms, kettle} = \frac{2000 \text{ W}}{340 \text{ V}} \approx 5.88 ext{ A}$

The total rms current is: $I_{total} = I_{rms, toaster} + I_{rms, kettle} \approx 2.35 + 5.88 \approx 8.23 ext{ A}$

9.1 A generator is shown below - NSC Physical Sciences - Question 9 - 2016 - Paper 1

Worked Solution & Example Answer:9.1 A generator is shown below - NSC Physical Sciences - Question 9 - 2016 - Paper 1

Is the generator above AC or DC? Give a reason for the answer.

Sketch an induced emf versus time graph for ONE complete rotation of the coil.

Calculate the rms current passing through the toaster.

Calculate the total rms current delivered by the generator.

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