Computing power factor and apparent power

Question

Question1)

Calculate dc voltage applied to the 10 Ω load resistor in acircuit shown below (assume diode threshold voltage is 0.7 V and bulk resistance is 0 Ω).

Question 2)

What value must R be in a circuit shown below to set up the diode current of 0.50 mA? (assume diode threshold voltage is 0.7 V and bulk resistance is 0 Ω).

 

Question 3)

Calculate base current entering each transistor, IB1 and IB2, and total current gain, β_total, for the following circuit (assume that each transistor is made from silicon and has the VBE of 0.7 V).

Question 4)

Factory has the maximum demand of 400 kW at a lagging power factor such that 600 kVAr of reactive power has to be supplied. Consider effect of adding capacitor banks in the two stages, each drawing 200 kVA_r leading. Calculate power factor and apparent power in each case:
a) without capacitive load
b) with one capacitive load of 200 kVA_r
c) with two capacitive loads of 200 kVA_r totalling 400 kVA_r

Question 5)

Using the summing operational amplifier, design 3-bit digital to analogue converter (DAC). Assume digital inputs are generated from the TTL circuit (logic 0 equal to 0 V, logic 1 equal to 5 V). Converter output must feed the speaker that has the maximum input voltage of 3.5 V. Draw the diagram of your completed circuit design and explain its operation.