Solving the Resistance of an Electric Water Heater

AI Thread Summary
To find the resistance of an electric water heater's heating element, the problem involves heating 137 kg of water from 20°C to 45°C in 16 minutes with a 220-V supply. The calorimetry equation Q = mcΔT is used to calculate the heat required, while the power can be expressed as V²/R multiplied by time. The discussion emphasizes combining calorimetry with electrical relations to derive the resistance. Participants suggest calculating the power based on the heat generated and the voltage applied. The hints provided guide towards a solution involving both thermal and electrical principles.
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Homework Statement


A well-insulated electric water heater warms 137 kg of water from 20°C to 45.0°C in 16.0 min. Find the resistance of its heating element, which is connected across 220-V potential difference.


Homework Equations


R=V/I


The Attempt at a Solution


Not sure how to approach this one. Should I refer to a calorimetry approach along with electrical relations? How might I start this one?

Any help/hints would be greatly appreciated.
 
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There is also an equation that relates the power to the voltage V and the resistance R.
On the other hand, you should be able to calculate the power from the given data.
 


Gotcha. Thanks for the hint. Looks like Q = mc delta T works great for calculating necessary heat to heat the water while v squared over R multiplied by time (in seconds) equals the heat generated by potential and resistance over time.

I appreciate your time in providing the hint.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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