The maximum peak-to-peak value of an AM wave is 45 V. The peak-to-peak value of the modulating signal is 20 V. What is the percentage of modulation? 

Consider the full-wave rectifier circuit as shown below with C = 474 F and transformer winding ratio of 14:1. If the input voltage is 120 VAC (RMS) at 60 Hz, what is the load resistor value for a peak-to-peak ripple less than 0.5 V? What is the output DC voltage? Assume ideal diode.

4.1 The current in an ac circuit at any time 𝑡 seconds is given by: 𝑖(𝑡) = 120 sin(100𝜋𝑡 +
0.36) amperes. Determine:
4.1.1 The peak value, the periodic time, the frequency and phase angle relative to
120 sin(100𝜋𝑡). 
4.1.2 The value of the current when 𝑡 = 0. 
4.1.3 The time when the current first reaches 60 A. 
4.1.4 The time when the current is first at maximum. 

Question 3  (IEIIQ16)

A 3 W rated Zener diode is used in a shunt voltage regulator circuit to supply a dc output of 12 V to a variable load with a minimum resistance of 240 Ω. The supply voltage varies between 20 V and 24 V.

3.1    Draw the circuit diagram.

3.2    Calculate the range of series resistance that may safely be used in this circuit. Select a single suitable standard value.

3.3    Calculate the maximum power rating required for the series resistor.

Question 4  (IEIIQ17)

A simple Zener voltage regulator is required to provide a steady regulated output voltage of 10 V under a maximum load of 80 mA, while the input voltage to the regulator varies between 12 V and 14 V.

17.1  Calculate the maximum rated current value of a Zener diode to be used

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

17.3  If a 5 W rated Zener were to be used in this circuit:

(i)      Calculate the maximum rated current value of a Zener device to be used

(ii)      Calculate the range of possible RS.  limiting resistor values.

(iii)     Suggest a suitable standard E12 resistor value