Recent content by Harrison01

Ok i understand that x and (x-1) are unitles numbers as we yet don't know their value but we do know that their value sums up to 10kohms. We therefore need to work out the ratio. We know we have a Vout of 3v and that Rl is 5kohms. I just can't seem to understand how we use all this data to give...

I just can't get in my thick skull...

So I'm thinking x=Vout/10kohms=3/10000=0.0003ma

Yeah Vout equals 3v and R is 10kohms

So by using the equation i have 9*Ra*5000/[(Rb*Ra)+(Rb*5000)+(Rb*Ra)] 9*x*R*5000/[((1-x)*R*x*R)+((1-x)*R*5000)+((1-x)*R*x*R)]

Yeah that's what i meant Gneil. Getting somewhere at least. Now i must be incredibly here thick but how can i carry out the maths if i don't have figures to put in the places of Ra & Rb. I just don't see how putting X or (1-X) helps. I understand that they are relevant to a ratio but if i...

Ok, round 2 Vout= E* Ra*Rl/(Rb*Rl)+(Ra*Rl)+(Rb*Ra)

Gneil, cheers for bearing with me. are you at your wits end yet? Ok, think I'm right here Vout=E*(Ra*(Rl/Ra+Rl))/(Rb+Ra/Ra)*(Rl/Ra+Rl) The only thing I'm still struggling to see here is how this will give me the values of Ra and Rb

Think I'm starting to wander off the track a bit here but still, here goes. Vout=E*Ra*Rl/Ra+Rl/Rb+Ra/Ra*Rl/Ra+Rl I know that Ra and Rb must equal a total of 10k ohms and the higher the Rb figure the higher the reistance and vice versa for Ra.

2 resistors in parallel is Rp=Ra*Rl/Ra+Rl.

Well the expression for Rp is Ra+Rl which would give me an equation of Vout=E*Ra+Rl/(Rb+Ra+Rl) I think...

Ok since we have realistically made our Parrallel resisters as one (Rp) our circuit has now become an open circuit or output voltage under no load condition with just 2 resitors in series, Vout=E*Rp/(Rb+Rp) but isn't this the same equation as my last post?

My expression for vout would surely be using the correct formula to give me the combined resistance of Ra & Rl but since i don't know the value of Ra how do i go about working it out? My equation for the Vout would be E*Ra/Rb+Ra=Vout but since we already know this is 3v there must be a way of...

how bad is this, xmas eve and I am frying mt brain tyring to get my head around this question. Ok, i under stand the equation and the working practice behind it all but the part I am struggling with is the ratio part. how do i go about working out the correct ratio of r1 and r2? Whatever...

Thanks Gneil. I haven't really covered many pots, I'm doing my HNC via open learning and the one thing I'm finding is that sometimes its hard to visualise things without it physically in front of you. So, because i have a pot with a wire connected to the wiper to some other point in the...