Answer to Question #37440 in Electric Circuits for Quamrul

Question

4 identical 1.5 volt cells were connected in series along with 3 ammeters,a lamp and a diode.The diode was forwardly biased.The lamp had a voltmeter connected across it which showed a reading of 2.6 V.The current in the circuit was 50 mA. A student expected the volmeter reading to be 6 V.The voltmeter was working correctly.Give 2 reasons why the reading on the voltmeter is less than 6.0 V.

Answer 1

4 identical 1.5 volt cells in ideal case really should give voltage 6.0 V. Nevertheless, a real volt cell has an internal resistance r which reduces output voltage as U = E - I*r. Another problems could make ammeters which also have their inner resistance and reduce voltage on the lamp.