00:01
Hi there, so for this problem we are told that a house loses energy through the exterior walls and ruth are the rate that is given and that is 5 ,000 joules per second.
00:16
This is the same as 5 kilowatts.
00:22
When the interior temperature is also given, so that temperature, let's call this the i, and that is, is equal to 22 celsius degrees.
00:39
And the upside, the temperature, let's call this the e for exterior, the temperature of the exterior is minus 5 celsius degrees.
00:53
So for part a of this problem, we are asked to calculate the electric power required to maintain the interior temperature 20 celsius degrees if the electric power is used in electric resistance heaters that convert all the energy transferred in by electrical transmission into internal energy.
01:20
Now, we know that the power, the electric power, is defined as the temperature, yes, the temperature, um, the temperature, um, the, for the energy transmitted electrically, let's call this dat, and this divided by the interval of time.
01:52
So all of the energy transferred into the heater by the electrical transmission becomes the internal energy.
01:59
So the power, the electric power, is just simply the value given, which is 5 kilo -waps.
02:11
So that's the solution for the first part of this problem.
02:17
And now for part b, so for this part we are asked about to calculate the electric power required to maintain the interior temperature at 22 celsius degrees.
02:33
If the electric power is used to drive an electric motor that operates the compressor of a heat pump that has a coefficient of performance that is 60 % of the carnet cycle value.
02:51
Now, let's see stand for the absolute temperature for a heat pump.
02:58
We know that that temperature is 295 kelvin.
03:15
Of course, this comes from the highest value to the temperature that is 20 celsius degrees.
03:22
We are passing this into kelvin, so remember that to pass this into kelvin, we need to add to this 273.
03:31
So this will give us 295 kelvin.
03:36
Now, so for a heat pump, we know that cop of the cardinant, the coordinate cop is equal to the ratio between this temperature divided by the change in the temperature.
03:56
So we will have that this is 295 kelvin and this divided by the difference in the temperature.
04:03
We know that this is the highest temperature, but the external temperature is the one that is given...