physics

An electric heater used to boil small amounts of water consists of a 25-Ω coil that is immersed directly in the water. It operates from a 60-V socket. How much time is required for this heater to raise the temperature of 0.50 kg of water from 29° C to the normal boiling point?

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asked by Dee
  1. i = V/R = 60/25 = 2.4 amps
    P = i v = 2.4*60 = 144 watts or Joules/second

    Joules into water = 144 t
    where t is in seconds

    144 t = C (.5)(100-29)
    I do not recall C, specific heat of water
    in Joules/ kilogram deg centigrade

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    posted by Damon
  2. t(seconds) = ((kg water)(temp change)(4186))/Watts

    Watts = V^2/ohms

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