1 for the Sinewave Below, Determine (A) the Rms Voltage (B) the Average Voltage (C) The

City University Degree Foundation in ICT &Electronics 2006/2007

5 questions set Time allowed – 90 Minutes Marks as shown

1 For the sinewave shown in Figure 1, determine (a) the rms voltage (b) the average voltage (c) the frequency (d) the instantaneous value of voltage after 3ms.

Figure 1 6 Marks

2 (a) Draw a scaled phasor diagram for the circuit in Figure 2. (b) From the phasor diagram, determine the (i) applied voltage (ii) phase angle

Confirm your answers in (i) and (ii) by calculation.

(c) Determine the useful power consumed in the circuit.

(d) If the supply frequency is 100Hz, determine the values of R, L, C

Figure 2 20 marks

3(a) Draw a scaled phasor diagram for the circuit in Figure 3 (b) From the phasor diagram, determine (i) Circuit current (ii) Power Factor

© Confirm your answers by calculation

(d) Determine the useful power consumed in the circuit

Figure 3 14 marks

-2-

4 (a) Draw a scaled phasor diagram for the circuit in Figure 4 (b) From the phasor diagram, determine (i) Applied Circuit Voltage (ii) Power Factor

Confirm your answers in (i) and (ii) by calculation

(c) If the supply frequency is 100Hz, calculate the value of the capacitor to be connected

across the RL circuit to bring the power factor up to unity. ( ie cos Ǿ =1)

Figure 4 20 marks

5 (a) Draw a scaled phasor diagram for the circuit in Figure 5. (b) From the phasor diagram determine : (i) Applied Circuit Voltage (ii) Power Factor .

Confirm your answers in (i) and (ii) by calculation.

(c) Determine the useful power consumed in the circuit.

(d) If the supply frequency is 200Hz, determine the values of R and L.

(e) Calculate the value of capacitor to be connected across the RL circuit to bring the power factor up to 0.98 leading

Figure 5 28 marks

Total 88 marks