Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply. When the voltage and current waveforms start at the same time, both have the same frequency, resulting in a zero phase angle. When any waveforms of electrical quantities start at the same time, reach their peak at the same time, pass through zero at the same time, and end at the same time, the two waves are in phase even though their amplitude may differ.

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Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply - NSC Electrical Technology Electronics - Question 3 - 2023 - Paper 1

Question 3

Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply. ... show full transcript

Worked Solution & Example Answer:Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply - NSC Electrical Technology Electronics - Question 3 - 2023 - Paper 1

Step 1

3.2 Refer to the AC waveforms in FIGURE 3.2 and draw the phasor diagram that represents them.

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Answer

The phasor diagram for the AC waveforms involves representing the voltage and current as vectors in a coordinate plane. The voltage phasor is represented as a horizontal vector along the real axis, and the current phasor is aligned with it because they are in phase. The angle between them is zero degrees, indicating no phase shift.

Step 2

3.3 Name TWO applications of resonance as applicable to tuned circuits.

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Answer

Radio tuning circuits - These circuits utilize resonance to select specific frequencies for radio broadcasts.
Television tuning circuits - Similar to radio circuits, these also use resonance to tune to specific channel frequencies.

Step 3

3.4 Identify the graphs below.

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Answer

3.4.1 - The graph in FIGURE 3.4(a) shows an impedance versus frequency response graph, indicating the relationship between impedance and frequency for a tuned circuit. 3.4.2 - The graph in FIGURE 3.4(b) represents the current versus frequency response, illustrating how current varies with frequency in a resonant circuit.

Step 4

3.5.1 Calculate the value of the supply voltage.

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Answer

To calculate the supply voltage ( V_{T} ), we use the formula:

V_{T} = \\sqrt{V_{R}^2 + (V_{L} - V_{C})^2}

Plugging in the values:

V_{T} = \\sqrt{30^2 + (60 - 20)^2} = \\sqrt{900 + 1600} = \\sqrt{2500} = 50 \\text{ V}.

Step 5

3.5.2 Calculate the phase angle.

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Answer

Using the formula for the phase angle ( θ ):

\tan θ = \frac{V_{L} - V_{C}}{V_{R}}

Calculating, we find:

θ = \tan^{-1}\left(\frac{60 - 20}{30}\right) = \tan^{-1}(1.33) = 53.13°.

Step 6

3.5.3 State whether the phase angle is leading or lagging.

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Answer

The phase angle is lagging because the voltage across the inductor is greater than the voltage across the capacitor.

Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply - NSC Electrical Technology Electronics - Question 3 - 2023 - Paper 1

Worked Solution & Example Answer:Describe what is meant by the term in phase with reference to the relationship between the applied voltage and current in an RLC circuit connected to an AC supply - NSC Electrical Technology Electronics - Question 3 - 2023 - Paper 1

3.2 Refer to the AC waveforms in FIGURE 3.2 and draw the phasor diagram that represents them.

3.3 Name TWO applications of resonance as applicable to tuned circuits.

3.4 Identify the graphs below.

3.5.1 Calculate the value of the supply voltage.

3.5.2 Calculate the phase angle.

3.5.3 State whether the phase angle is leading or lagging.

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