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5.1 A capacitor with a capacitive reactance of 250 Ω, an inductor with an inductive reactance of 300 Ω and a resistor with a resistance of 500 Ω are all connected in series to a 220 V/50 Hz supply - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

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5.1 A capacitor with a capacitive reactance of 250 Ω, an inductor with an inductive reactance of 300 Ω and a resistor with a resistance of 500 Ω are all connected in... show full transcript

Worked Solution & Example Answer:5.1 A capacitor with a capacitive reactance of 250 Ω, an inductor with an inductive reactance of 300 Ω and a resistor with a resistance of 500 Ω are all connected in series to a 220 V/50 Hz supply - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

Step 1

5.1.1 Calculate the total impedance of the circuit.

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Answer

To calculate the total impedance (Z) of the circuit, we use the formula:

Z=R2+(XLXC)2Z = \sqrt{R^2 + (X_L - X_C)^2}

Substituting the given values:

Z=5002+(300250)2Z = \sqrt{500^2 + (300 - 250)^2}

This simplifies to:

Z=5002+502=250000+2500=252500Z = \sqrt{500^2 + 50^2} = \sqrt{250000 + 2500} = \sqrt{252500}

Therefore, the total impedance is approximately:

Z502.49 ΩZ \approx 502.49 \ \Omega

Step 2

5.1.2 Calculate the power factor of the circuit and state whether it is leading or lagging.

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Answer

The power factor (cos θ) can be calculated using:

cosθ=RZ\cos \theta = \frac{R}{Z}

Substituting the values we have:

cosθ=500502.490.995\cos \theta = \frac{500}{502.49} \approx 0.995

Since the circuit is in a series configuration with an inductor, it results in a lagging power factor. Thus, the power factor is approximately 0.995 and it is Lagging.

Step 3

5.2.1 The resistance of the 60 watt 110 V lamp.

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Answer

Using the power formula:

R=V2PR = \frac{V^2}{P}

Substituting the known values:

R=110260=1210060201.67 ΩR = \frac{110^2}{60} = \frac{12100}{60} \approx 201.67 \ \Omega

Step 4

5.2.2 The total current flowing through the circuit.

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Answer

We can find the total current (I) through the circuit using:

I=PVRI = \frac{P}{V_R}

Substituting the values:

I=601100.545 AI = \frac{60}{110} \approx 0.545 \text{ A}

Step 5

5.2.3 The impedance of the circuit.

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Answer

To calculate the impedance (Z), we use:

Z=VIZ = \frac{V}{I}

Substituting the values:

Z=2200.545403.67 ΩZ = \frac{220}{0.545} \approx 403.67 \ \Omega

Step 6

5.2.4 The inductance of the inductor.

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Answer

The inductive reactance (X_L) can be calculated using:

L=XL2πfL = \frac{X_L}{2\pi f}

First, rearranging:

XL=Z2R2X_L = \sqrt{Z^2 - R^2}

Then substituting the calculated values:

XL=4002201.672X_L = \sqrt{400^2 - 201.67^2}

Now, substituting into the inductance formula yields:

L=XL2πf100.692π(50)1.1 HL = \frac{X_L}{2\pi f} \approx \frac{100.69}{2\pi (50)} \approx 1.1 \text{ H}

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