167. What refers to the lowest voltage across any insulator that can cause current flow?

The voltage across a 5 μF capacitor is known to be Vfort≥0 , where t is in seconds.

Part B

Find the power at the terminals of the capacitor when t = 185 μs .

Part D

Find the energy stored in the capacitor at t = 185 μs

Part E

Find the time when the maximum energy stored in the capacitor occurs.

Part F

Find the maximum energy stored in the capacitor

Question 1

A simple Zener diode shunt voltage regulator is to supply 12 V to a load which normally draws a load current which varies from 0 to 50 mA. The input voltage varies between 15 V and 18 V.

1.1 Calculate the maximum rated current value of a Zener device to be used.

1.2 Calculate the minimum power for the Zener that could be used safely.

1.3 If a 5 W rated Zener were to be used, calculate the range of possible RS. values and hence suggest a suitable standard E12 resistor value.

1.4 State four (4) conditions under which a Zener diode dissipates minimum power in a regulator circuit.

Question 2 (IEIIQ15)

A 2.5 W Zener diode is used in a simple Zener shunt voltage-regulator to supply 5.1 V to a load which normally draws a load current varying from 0 to 125 mA. The input voltage varies between 8 V and 9.5 V

2.1 Give two (2) reasons for the inclusion of the series resistor in the Zener-regulator circuit.

2.2 Calculate the range of series resistance that may safely be used in this circuit.

2.3 Select a single suitable standard E12 resistor value and give its colour code with 1 % tolerance.

Kindly solve the below questions:

1. Assume the AC frequency is 50 Hz. Convert these phasors to signals (remember that phasor magnitudes are RMS values of the signals)

    (a) V = 115∠90V

    (b) I = 10 + 10j A

2.  Convert these signals to phasors (remember to us RMS values for the phasor magnitude)

    (a) v(t) = 230cos (314t + 20) V

    (b) i(t)  = 5cos (314t + 10) A

3. Suppose the voltage across a load is v(t) and the current drawn is i(t) where 

v(t) = 230cos (314t + 20) V

i(t)  = 5cos (314t + 10) A

   (a) calculate the complex power, real power, reactive power and apparent power.

   (b) calculate the power factor and indicate if it is leading or bagging