question_answer

In the circuit diagram given, a voltmeter \[\mathbf{V}\] is connected across a lamp L. What changes would occur at lamp L and voltmeter V, if the resistor R is reduced in value? Give reason for your answer.                        

Answer:

                    If the value of the resistance R is reduced, the current in the forward biased input circuit increases. The emitter current \[{{I}_{E}}\] and the collector current \[{{I}_{C}}({{I}_{C}}={{I}_{E}}-{{I}_{B}})\] both increase. The lamp L glows more brilliantly. Due to the increase in \[{{I}_{C}}\], the potential drop cross the lamp L increases and hence the voltmeter V indicates a higher voltage.