1. Tardigrade
  2. Question
  3. Physics
  4. A projector lamp can be used at a maximum voltage of 60 V, its resistance is 20 Ω , the series resistance (in ohms) required to operate the lamp from a 75 V supply is

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A projector lamp can be used at a maximum voltage of 60 V, its resistance is 20 $ \Omega $ , the series resistance (in ohms) required to operate the lamp from a 75 V supply is

EAMCETEAMCET 2008Electromagnetic Induction

Solution:

Current flowing through the lamp, $ I=\frac{V}{R}=\frac{60}{20}=3A $ The current in the lamp must remain 3A, when it is operated at 75 V supply. Let R be the resistance connected in series, then $ \frac{75}{20+R}=3 $ $ \Rightarrow $ $ 75=60+3R $ or $ 3R=75-60 $ or $ 3R=15 $ or $ R=5\Omega $