Tutorial Exercise A well-insulated electric water heater warms 116 kg of water from 20.0° C to 42.0° C in 24.0 min. Find the resistance of its heating element, which is connected across a 240-V potential difference. Part 1 of 5 - Conceptualize We expect the water heater to be high-powered compared to other household appliances. For the power to be on the order of kilowatts, the current would be several amperes and the resistance only a few ohms. Part 2 of 5 - Categorize We will find the energy required to heat the water. Then we will find the power of the heating element and calculate its resistance from the power and the potential difference. Part 3 of 5 - Analyze We know the mass of water m and the temperature change AT. The specific heat of water is c = 4 186 J/kg • °C. For the energy input by heat, we have Q = mcAT 116 116 kg) (4 186 J/kg · °C) ( 22 22 °c) = 1.068 1.07 x 10'J. Part 4 of 5 - Analyze If the tank is well-insulated, essentially all of the energy electrically transmitted to the heating element becomes internal energy in the water and we can equate the energy input by heat to the electrical energy transmitted, that is, Q = Eelec.Thus, the power supplied by the heater is elec = At P = At x 107 w. Submit Skip (vou cannot come back)

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Tutorial Exercise
A well-insulated electric water heater warms 116 kg of water from 20.0° C to 42.0° C in 24.0 min. Find the
resistance of its heating element, which is connected across a 240-V potential difference.
Part 1 of 5 - Conceptualize
We expect the water heater to be high-powered compared to other household appliances. For the power to be
on the order of kilowatts, the current would be several amperes and the resistance only a few ohms.
Part 2 of 5 - Categorize
We will find the energy required to heat the water. Then we will find the power of the heating element and
calculate its resistance from the power and the potential difference.
Part 3 of 5 - Analyze
We know the mass of water m and the temperature change AT. The specific heat of water is
C = 4 186 J/kg · °C. For the energy input by heat, we have
Q = mcAT
|116
116 kg ) (4 186 J/kg • °C) (22
22 °C
|1.068
107 J.
1.07
Part 4 of 5 - Analyze
If the tank is well-insulated, essentially all of the energy electrically transmitted to the heating element
becomes internal energy in the water and we can equate the energy input by heat to the electrical energy
transmitted, that is, Q = Eolec:Thus, the power supplied by the heater is
Q
E elec
P =
%3D
At
At
x 107
W.
Submit
Skip (you cannot come back)
Transcribed Image Text:Tutorial Exercise A well-insulated electric water heater warms 116 kg of water from 20.0° C to 42.0° C in 24.0 min. Find the resistance of its heating element, which is connected across a 240-V potential difference. Part 1 of 5 - Conceptualize We expect the water heater to be high-powered compared to other household appliances. For the power to be on the order of kilowatts, the current would be several amperes and the resistance only a few ohms. Part 2 of 5 - Categorize We will find the energy required to heat the water. Then we will find the power of the heating element and calculate its resistance from the power and the potential difference. Part 3 of 5 - Analyze We know the mass of water m and the temperature change AT. The specific heat of water is C = 4 186 J/kg · °C. For the energy input by heat, we have Q = mcAT |116 116 kg ) (4 186 J/kg • °C) (22 22 °C |1.068 107 J. 1.07 Part 4 of 5 - Analyze If the tank is well-insulated, essentially all of the energy electrically transmitted to the heating element becomes internal energy in the water and we can equate the energy input by heat to the electrical energy transmitted, that is, Q = Eolec:Thus, the power supplied by the heater is Q E elec P = %3D At At x 107 W. Submit Skip (you cannot come back)
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