ELECTRICITY AND ELECTRONICS

PART I

Answer all questions.

Question 1

(a) With reference to vacuum tubes define the following terms: [2]
(i) Grid cut off voltage;
(ii) A.C plate resistance.
(b) Calculate the mutual conductance (gm) of a triode if amplification factor (μ)=20 and plate resistance (rp) =8000Ω. [2]

Question 2

(a) Draw a neat diagram to show that diode works as a half wave rectifier. [2]
(b) State any two causes for failure of vaccum tube. [2]

Question 3

(a) What is the value of the ripple factor for the following: [2]
(i) Half wave rectifier;
(ii) Full wave rectifier.
(b) State two main functions of bleeder resistor used in the regulated power supply. [2]

Question 4

Draw a neat diagram of a crystal microphone. Mention one important quality this crystal should possess. [4]

Question 5

(a) Obtain the relationship between the root mean square (rms) of current (Irms) and its peak value (Im). [3]
(b)Write any one difference between electrolytic and non-electrolytic capacitor. [1]

Question 6

Write short notes on the following: [4]
(a) Pendant holder;
(b) Distribution board.

Question 7

A full wave rectifier uses two diodes (Figure - 1). The internal resistance of each diode may be assumed constant at 20Ω. The transformer (rms) secondary voltage is 50V and the load resistance is 980 Ω.

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