MCQ 8: A single-phase full-wave rectifier has an input voltage of 20 V (RMS). The frequency of the supply is 50Hz. A capacitor is used to smooth the output voltage of the rectifier. The rectifier now needs to supply a constant current of 5 mA to the load. The ripple has to be kept at 25 mV (peak). Calculate the value of the capacitor. (2) a) 4 mF b) 2 mF c) 1 mF d) 5 F MCQ 9: To add one 3-bit number to another 3-bit number, we need: a) One half adder and two full adders b) Two half adders and two full adders c) One half adder and three full adders d) Two half adders and one full adder (2) MCQ 10: The result of 1111;+1001; (Hint: the index 2 denotes the binary representation) is: (2) a) 10110 b) 11000, c) 10100; d) 01000, st1 MCQ 11: If the current i(t) = (0, 1 st 2 flows through a resistor with resistance R, what is the average power dissipated from the resistor from 1-0 to 1-2? (2) a) 2R b) R c) R d) 8R MCQ 12: Calculate the value of the capacitance required to correct to a new power factor of 0.9 lagging of a single-phase motor with the following parameters: (2) V=3.3 kV P=150 kVA pf = 0.8 lagging a) 26.3 F b) 12.7 F c) 9.3 F d) 22.3 F f=50 Hz MCQ 13: Which one of the following statements is not true: a) Semiconductors are materials that have a resistivity in the range between conductors and insulators b) N-doped semiconductors have more conduction electrons than holes c) When forward biased, a diode behaves like a closed switch d) Placing n-type semiconductors adjacent to p-type semiconductors yields a symmetric behaviour a) 0.94 b) 0.63 c) 0.77 d) 0.82 (2) MCQ 14: An industrial load (Figure 2) consists of a single-phase 150 kVA load operating at a power factor of 0.55 lagging as well as a single-phase 100 kVA load operating at a power factor of 0.75 leading. Calculate the overall power factor. (2)