Help pls:To show that the amt of energy supplied by a heating coil in water (E=Pt=VIt) is equal to the energy?

Question

...absorbed by the water (H=mc▲T).

I need to write up and perform a first hand investigation with the aim above...

any ideas/ tips?? warnings?

any help will be much appreciated =]

Answer 1

Put in say 100ml of water into the kettle. Measure it's temperature.

Turn the kettle on, and start your stop watch.

Keep watching your thermometer until the water gets to say.. .90 degrees celcius.  Stop your stopwatch.

Now you some calculations.

The Energy supplied by the Kettle is:

E = Pt  = Power rating of your kettle * time on your stop watch.

The energy absorbed by the water is:

E = mc(Tf - Ti)

   = 0.1kg * 4180 * (90-starting temp of your water)

The two answers should be equal.

Unfortunately, in the real world they won't be equal, because your kettle is not 100% efficient.  That means that some of the electrical energy that is consumed by the kettle was not converted to heat energy to heat the water.  It was lost/wasted somehow.  

So if you want to go even further... do the above investigation a few times with different amounts of water... say 100ml, 250ml, 500ml and 1000ml....

Find the energies of the kettle (x) and energies for water (y)... Plot them on a graph...  You should get a straight line (line of best fit)

The gradient of that line should give you the kettle's efficiency rating (x100 to convert to %)... Good luck.