Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Basic electricity & incandescent bulb numericals

  1. Jan 31, 2009 #1
    hi there, i hav few questions:

    1. A 12V, 24W tungsten filament bulb is supplied with current from n cells connected in series. Each cell has an emf of 1.5V and internal resistance of 0.25. What is the value of n in order that the bulb runs at its rated power?

    2. Three bulbs are rating 40W, 60W, 100W designed to work on 220V mains. Which bulb will burn most brightly if they are connected in SERIES across 220V mains? Repeat the same question when they are connected in PARALLEL across 220V.

    3. An electric iron is marked 20 Volts, 500W. what will be The units consumed by it in using it for 24 hours?

    4. What is the heat generated by a 40 W bulb in one hour?

    please someone help me wid these numericals, i wud be highly grateful!
  2. jcsd
  3. Jan 31, 2009 #2


    User Avatar
    Homework Helper

    Show some workout.
    Can you find out the relation between V, W, I and R?
  4. Jan 31, 2009 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    flabber, welcome to PF :smile:

    In addition to showing your own efforts towards solving the problem, please post separate questions in separate threads. If we had 4 problem discussions all running at once, it would be too confusing to follow.

    I'll suggest you make 4 separate new posts, one for each problem. Also, please show what equations you think are relevant (as rl.bhat suggested), and show your own attempt or start toward solving each problem.
    Last edited: Jan 31, 2009
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook