At the end of lab, submit your .java file via WebCT,
under the assignment “lab-quiz1”.
The deadline is 50 minutes after the hour, sharp! (I'll give 5-min and 2-min warnings.)
This lab-quiz is individual work,
but you can use any notes you like,
and you can use a web browser to access anything on the itec120 web page
(previous labs, etc).
Some handy ones might include
lab01
and
lab01-soln.
Do not search the web for other people's programs.
(And duh: no chat windows, IM, email, etc.)
As usual, you can use BlueJ to make a new Project and new Class, but you'll want to gut the template it gives you and replace it all with something like
class TempConverter { } |
h(5) = 23 /* Well, instead of 'h', use your particular function name. */ h(0) = 14 ... |
In some odd countries (namely, Canada, and most of the rest of the world), temperatures are measured in degrees Celcius, instead of degrees Fahrenheit. So when you are traveling and you look in the newspaper and see a forecast for 22°C, it might sound chilly until a friendly Canadian citizen tells you that this is a balmy 71.6°F.
Some other notable temperatures1 are freezing (0°C, which is 32°F), and boiling (100°C, which is 212°F).
The general case for converting degrees-Celcius into degrees-Fahrenheit is given by the arithmetic formula
F(C) = 9⁄5 · C + 32
Write a java function celcToFahr, which takes a temperature in °C, and returns that temperature expressed in °F.
You read in a science article that the surface of the sun is 5700K (“kelvins”2), and that absolute zero is (conveniently) 0K. These numbers seem even more baffling, until that same cheerful Canadian tells you that to convert a temperature from Kelvins to °C, you simply subtract 273.15. So 0K (absolute zero) is -273.15°C, which in turn is -459.67°F, brr. Similarly, 273.15K (freezing) is 0°C which (as we've seen earlier) is 32°F.
Write a function kelvToFahr to convert temperatures in Kelvins to
temperatures in °F.
Hint: For a test case -- what is 373.15K, in °C and in °F?
What steps did you follow, to figure out the answer?
Can you write code which follows those same steps?
1 One other intriguing test case is that -40°C = -40°F. Is it some mystical coincidence, that two scales exactly meet at such a nice round number, instead of some random number with a bajillion decimal places?
Well, it is a small bit of luck that the answer is an integer, but every integer celcius temperature corresponds to an even fifth-of-a-fahrenheit temperature, because of the 9/5 in the formula. Where does 9/5 come from?
The factor of 9/5 stems from the difference between freezing and boiling in the two systems: (212-32)/(100-0) = 180/100 = 9/5. Both scientists Fahrenheit and Centigrade set integers for the freezing and boiling of water, so that there'd be an integer number of notches on their thermometer between the two. This is the ultimate reason why conversions between the two systems use rational numbers, and not some long irrational real number arising randomly from nature.
If some martians came to Earth and (fascinated by all the ambient water) decided that they would invent a new temperature scale where the freezing point of water was declared as -27°Martian and the boiling point as 123°Martian, we'd still end up with a conversions which used fractions, not irrationals. back2Interestingly, you don't write or say “degrees” with the Kelvin scale; the unit of temperature has just a one-word name rather than a two-word name. back
©2006, Ian Barland, Radford University Last modified 2006.Sep.21 (Thu) |
Please mail any suggestions (incl. typos, broken links) to ibarlandradford.edu |