Radio,Television And Electronic Paper 2, May/June 2015

Question 1

    (a) sketch the circuit symbol for the following components:

    (i)crystal diode; (ii)NPN transistor.

    (b)        State Ohm’s law.
    (c)        The instantaneous voltage applied to a circuit is expressed as
    .
    Calculate the:

  1. r.m.svalue;
  2. peak-to-peak value;
frequency of the voltage.

Observation

The expected answers were:
            (a) (i) Crystal diode
           Basic diagram of any/specific diode ( Zener, LED etc)

       (ii) NPN transistor

(b)        Ohm’s law states that the current flowing in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance provided the temperature remains constant.
OR
Ohm’s law states that the current flowing through a metallic conductor is directly         
proportional to the applied voltage provided the temperature (and other physical quantities)  remain constant.    

  •                                                                              

       Mathematical expression without constants

( c)  .


= 42.4V.                                                                           

                        = 2 x 60                                                  
= 120V.                                                             


                                                                     
The question was well answered by candidates.