https://www.physicsforums.com/showthread.php?s=&threadid=7593

ok, im taking engineering physics II ... unfortunately, im forced to take this as part of my COMPUTER SCIENCE degree ... (why i have no idea..stupid, as i dont really care how many newtons of force it takes me to push a key on the keyboard, and how much current it takes to go from the keyboard to the computer to put the key on the screen) .... sorry, just im not the most science-oriented person. which is why im not a computer engineer.

so i have a question.

the question on my homework is this:

A sloar cell generates a potential difference of 0.10V when a 500-Ohm resistor is connected across it and a potential difference of 0.16V when a 1000-Ohm resistor is substituted. What are (a) the internal resistance and (b) the emf of the sloar cell? (c) The area of the cell is 5.0 (cm^2). What is the efficiency of the cell for converting light energy to internal energy in the 1000-Ohm external resistor?

question. What is the difference between the potential difference, and its emf? i know V=IR . isnt the total V what comes out of the power source? and isnt the emf the power source? I'm lost on what this is.

also, for part c ... how would i approach in solving this? The chapter deals with the circuits, resistors, etc. but effeciency?

any help would be appreciated!

thanks