Hi. My group and I did a practical the other day and we have to write a lab report on it using our data and the data of another group. The steam boiler creates steam which is fed through a nozzle to a turbogenerator. The generator creates electricity, and this is fed into a loop with a potentiometer, like this: http://i.imgur.com/auKVlzP.png The strange thing is that for our group's data, the highest potentiometer setting gives the lowest efficiency. While for the other group's data, the highest setting gives the highest efficiency. AFAIK a potentiometer is simply a variable resistor. What should be expected? If I know what to expect I will be able to understand who went wrong and where (probably). Thanks for the help.