How to Calculate Resistors in Series and Parallel

What is the equivalent resistance of the three resistors in series with the following values: R1 = 10 Ω, R2 = 20 Ω, and R3 = 5 Ω (Give only the numeric part of your answer.)

Can u guys hep me? Please thanks for the response :>

Hi, without seeing how your classmate is arriving at an answer it is impossible to say. However, this is the correct way and if you do it this way you know that you will arrive at the correct answer. I hope this helped.

Hi! I'm confused because the method my classmate use in solving Parallel Resistors are different from this. I prefer this method because I can understand it well and used this when I'm in Grade 5. So my question is do we get the same answer if I use this method and my classmates will use the method where they will find its denominator?

thank you

Hi!

hi mark

Hi, there is a worked example that shows how to insert your values into the formula and how to take it forwards to an answer. Which bit of the process isn't clear, perhaps we can look at editing the example to highlight this.

no explanation on the calculation for the 3 parallel resistor, pointlesss, just hocus pocus and assume everyone gets it

nice calculations

Really I will your instructions is a very helpful .thanks a lot sir

Just for fun: task 3 example 1 should be 6 Ohms Also formula for two res in paralel and for more than 2 is exactly the same – if you use the latter for two, but solve it with vulgar fractions without finding smallest denominator, you will get the same formula. So, its also possible to make formulas for each on n numbers of resistors, but its impractical for normal use. P.e. for 3 res Rtot=R1xR2xR3/((R1xR2)(R2xR3)(R1xR3))

Hi, thanks for getting in touch. The information that you require is included in the above tutorial. Where it says 'and so on', this indicates that the process is the same for additional resistors. I hope this helps.

How to calculate the value of 3 and more resistors in parallel and elaborate the same.

Hi Ian, it's difficult to visualise your circuit without seeing it but I will give an answer based on what I think you have. Firstly, you will need to work out the value of the three resistors in parallel (the formula is on the page above). Then, once you have this value you then need to do an in series calculation using the resistor on its own and the result of the first calculation you did to give the total resistance for the circuit. I hope this helps.

I need your help to find the correct formula . I have 3 parallels and one other on its own. I’m sorry I don’t know the correct terminology but all have a value of 60 ohms . I got an A side and B side : on the A side I have the 60 alone and on the B side I have 3 – 60 ohms. I’m pretty good at math but the formula is missing here. Please help me with a formula to figure out the total resistance

This is awesome

thanks,mark.

Hi Yonela, yes you need to use a different formula as is shown in the worked examples.

for parallel circuit with two resistor we only use that formula in task 2 we do not use it when we have three or more resistors?

Hi Bill, you would use the series calculation first to find the combined resistances. So, in this case, R1 becomes R1Total and R2 becomes R2Total and you can then do the parallel calculation as normal. I hope this helps.

so for parallel circuits with >2 resistors, there is no algebraic equation derived that we can use. We only do the specific calculation to find the specific answer every time?

Hi Tom, If your target is 15 the calculation would look like; 1/15 = 1/48 + 1/80 + 1/R. Then rearrange the formula for R, it becomes; 1/15 – 1/48 – 1/80 = 1/R.

Hi i read this reply to colin and didnt quite understand. What do you do once you have the reciprical values for example my taget is 15 i have 2 resisitors 48 and 80. Recipricals are 1/48=0.208333333 and 1/80=0.0125 what do i do from here?

very important in my training.

This is very helpful,thank you for the initiative

Hi Colin, Simply work the formula backwards. For series start with the value you want to achieve, subtracting values you have as you go until you reach 0. For parallel what we're dealing with is reciprocal numbers, and they can be reversed. For example 1/33 = 0.30303. 1/0.30303 = 33. So start with the value you want to achieve. Take a resistor value you have and divide 1 by that value to get the reciprocal number. Rob

What is the formula if I know what resistance I want to achieve but don't have the correct value available. But I do have lots of other value resistors that I might be able to use?

HI Elias, It comes down to rounding. We rounded to three significant figures, but if you round shorter than that you will see an answer of around 6, so you have done it right. Given the value of standard resistors anyway in this case you would probably use 6.8 Ohms. Hope that helps.

Hi! I was just wondering about these parallel resistor equations. Isn't the answer to Task 3 question 1 suppose to be 6 instead of 5.95? Or am I just totally lost here? Have a good one!