(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Power microwave problem?

A 1000W microwave oven heats 500 g of water from 10.0 degrees Celsius to 55.0 degrees C in a time of 2 min. the heat capacity of water is 4200 J/kgdegrees C

2. Relevant equations

have i done this properly? there are 4 other questions with this

3. The attempt at a solution

P=1000W

m=0.5kg

T1=10.0C

T2=55.0C

change in T=45C

t=120s

c=4200J/kg degress C

a) how much thermal energy did the water gain?

have i done this correctly

Q=mcT

=(.5kg)(4200 J/kgC)(45C)

=94500 J

Q=9.5 x 10^4 J

b)How much power was associated with this thermal energy?

have i done this correctly

P=E/t

=9.5x10^4 J / (120s)

P=787.5 W

c) What percentage of the electricity power that went into the microwave actually went into heating the water?

Did i do this correctly

787.5 W / 1000 W x 100

= 79%

d) Why didn't all the electricity energy of the microwave get converted to thermal energy of the water?

Because loss of energy was also due to opperating the microwave and making cup of water spin

What are other reasons?

Thanks!

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# Homework Help: Microwave energy problem (please check my answers)

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