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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


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    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)

    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 ©)
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