Q. In the following circuit, a voltmeter $V$ is connected across a lamp $L$. What change would occur in voltmeter reading if the resistance $R$ is reduced in value
A) Increases
B) Decreases
C) Remains same
D) None of these
Explanation
(a) Here the emitter base junction of $N$-$P$-$N$ transistor is forward biased with battery $V_{BB}$ through resistance $R$. When the value of $R$ is reduced, then the emitter current $i_{e}$ will increase. As a result the collector current will also increase. ($i_{c} = i_{e} - i_{b}$). Due to increase in $i_{c}$, the potential difference across $L$ increases and hence the reading of voltmeter will increases
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.