1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Current and Watts

  1. Jul 15, 2011 #1
    Can you determine current given only the watts?

    Ex) if you have a lightbulb with 120 Watts, can you determine the current (charge) that flows through it in a second, for example?
     
  2. jcsd
  3. Jul 15, 2011 #2

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    Nope.
    In a low voltage circuit, you need a lot of current to produce the same power as for a high voltage circuit.
    Remember - Power (Watts) = Volts (Volts) X Current (Amps)
     
  4. Jul 15, 2011 #3
    From the way the question is phrased, no was the correct answer.
    You need any 2 (Voltage/Current/Resistance/Power) to determine an unknown in basic circuits.

    However, if you MEANT (since you referenced a 120W light bulb) how much current will the bulb draw on a standard 120 VAC circuit, then that is simply P=V*I ---> I = P/V = 120W/120V = 1 Amp.

    A 120 W rated bulb will not actually draw/dissipate 120 W of power unless it is powered by the expected voltage (ie a 12V battery will not push 10 amps through it).
     
  5. Jul 15, 2011 #4

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    In general no, you need also voltage:
    Power = voltage times current.

    In the lightbulb example you probably know the voltage implicitly i.e. it's a lightbulb used with 120V AC house lights. In that case you would solve to find the current is 1 amp (1 coulomb per second).

    current = power / voltage
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Current and Watts
  1. Kelvin and Watts (Replies: 14)

  2. Watt is it? (Replies: 1)

  3. Watts and Acceleration (Replies: 10)

  4. Watt is going on? (Replies: 4)

  5. Joules and watts (Replies: 7)

Loading...