5.1 Describe the term impedance with reference to an RLC circuit. 5.2 FIGURE 5.2 below shows the phasor diagram of a series RLC circuit. Answer the questions that follow. 5.2.1 With reference to current and voltage, explain whether the circuit is inductive or capacitive. 5.2.2 Describe how an increase in frequency will affect $V_L$. 5.2.3 Calculate the total voltage. 5.3 The parallel circuit in FIGURE 5.3 below consists of a capacitor that draws a current of 4 A, an inductor that draws a current of 6 A and a resistor that draws a current of 5 A. The components are connected to a 240 V/50 Hz supply. Calculate the: 5.3.1 Total current. 5.3.2 Phase angle. 5.3.3 Inductive reactance.

NSC Electrical Technology Electronics Resonance: 5.1 Describe the term impedance

5.1 Describe the term impedance with reference to an RLC circuit - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

Question 5

5.1 Describe the term impedance with reference to an RLC circuit. 5.2 FIGURE 5.2 below shows the phasor diagram of a series RLC circuit. Answer the questions that f... show full transcript

Worked Solution & Example Answer:5.1 Describe the term impedance with reference to an RLC circuit - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

Step 1

5.1 Describe the term impedance with reference to an RLC circuit.

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Answer

Impedance is defined as the total opposition offered to the flow of current when an RLC circuit is connected across an alternating voltage supply. It combines resistance and reactance in a circuit, affecting how current and voltage behave.

Step 2

5.2.1 With reference to current and voltage, explain whether the circuit is inductive or capacitive.

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Answer

In the phasor diagram, the voltage across the inductor, $V_L = 80 V$ , is greater than the voltage across the capacitor, $V_C = 50 V$ . This leads to a situation where the current $I_T$ will lag the voltage $V_S$ , indicating that the circuit is inductive.

Step 3

5.2.2 Describe how an increase in frequency will affect $V_L$.

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Answer

If the frequency of the supply is increased, the inductive reactance $X_L$ of the coil will also increase, as $X_L$ is directly proportional to the frequency of the supply. This results in an increase in the voltage across the inductor $V_L$ .

Step 4

5.2.3 Calculate the total voltage.

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Answer

The total voltage $V_T$ can be calculated using the formula:

ho imes ext{Resultant Voltage}$$ where the resultant voltage is given by: $$V_f = rac{1}{ ho} imes ext{Square Root of } [ (V_R)^2 + (V_L - V_C)^2 ]$$ Substituting the values: $$V_T = ext{sqrt}(110^2 + (80 - 50)^2) \\ = ext{114.02 V}$$

Step 5

5.3.1 Total current.

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Answer

To find the total current $I_T$ , we apply the formula: $I_T = ext{sqrt}(I_R^2 + (I_L - I_C)^2) \\ = ext{sqrt}(5^2 + (6 - 4)^2) \\ = 5.39 A$

Step 6

5.3.2 Phase angle.

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Answer

The phase angle $\theta$ can be calculated using: $\theta = \cos^{-1}\left(\frac{I_R}{I_T}\right) \\ = \cos^{-1}\left(\frac{5}{5.39}\right) \\ = 21.93^\circ$

Step 7

5.3.3 Inductive reactance.

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Answer

The inductive reactance can be calculated using: $X_L = \frac{V_T}{I_L} \\ = \frac{240}{6} \\ = 40 \Omega$

5.1 Describe the term impedance with reference to an RLC circuit - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

Worked Solution & Example Answer:5.1 Describe the term impedance with reference to an RLC circuit - NSC Electrical Technology Electronics - Question 5 - 2017 - Paper 1

5.1 Describe the term impedance with reference to an RLC circuit.

5.2.1 With reference to current and voltage, explain whether the circuit is inductive or capacitive.

5.2.2 Describe how an increase in frequency will affect $V_L$.

5.2.3 Calculate the total voltage.

5.3.1 Total current.

5.3.2 Phase angle.

5.3.3 Inductive reactance.

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