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: Heater and stuff

  1. Sep 26, 2004 #1
    A heater has a resistance of 15.0 W. It operates on 120.0 V. What thermal energy is supplied by the heater in 30.0 seconds? Answer must be in Kilo-joules.


    Well o_o ..it would be nice if you could try to help me with this question. Since I recently moved from Germany to the U.S. with my parents.. and we weren't at this point in my old school.
     
  2. jcsd
  3. Sep 26, 2004 #2

    Tide

    User Avatar
    Science Advisor
    Homework Helper

    Do you mean 15 Ohms resistance?

    Use Ohm's Law to calculate the power usage (voltage times current) and note that energy = power times time.
     
  4. Sep 26, 2004 #3
    Voltage (volts) = Current (amps) x Resistance (ohms)
    Power (watts) = Voltage (volts) x Current (amps)

    Therefore:
    Resistance (ohms) = Power (watts)

    Energy Transfer (J) = Power (W) x Time (s) => E = 15 x 30
    => Answer should be 450 J or 0.45 kJ.

    The Bob (2004 ©)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook