# Potential Divider Circuits – A Level Physics

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Published on May 30, 2015 by

These are not too bad - just follow the basic rules or circuits and you can solve any problem. These potential divider circuits divide the potential and are often used with thermistors or LDRs as a sensing circuit.

Thanks for watching,

Lewis

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• Wow that was so clear

• If only you posted this before my Unit 1 exam 🙁

• aleryani 98

• He posted this 2 years ago.. you commented 1 year ago… BOI.

• Thank you very much, couldn’t understand potential dividers at all until now.

• Kuddos to you big sir, you’re the best I’ve seen some far 🙂 keep up the good work. Cheers

• Thank you!!!

• what was that at 1:49 to 1:52 ??

• +Dr. Fhood Kirchhoff’s First Law:

• @A Level Physics Online thanks

• kirchoff’s first law

• I’ve been looking everywhere but I still can’t find an answer to my question.
I am currently studying the OCR AS level (spec A) physics course and there’s a part on “Wheatstone circuits with a strain gauge”:
In the book they give you an equation for calculating the output voltage of the circuit, but it has missing symbols 🙁 (there’s an error in the textbook).

(there’s the picture of the equation and circuit)

• +awesomeoverawesome Answer to question 3.

Initially when all resistors are 100 ohms the circuit is ‘balanced’ and the output voltage is 0. Because V = ((100/200) – (100/200))x 6 = 0

When there is a 0.001% change to 100.1ohms across R1 then the pd is equal to 0.0015V

Is that right?

• @A Level Physics Online Thank you so much for all your responses, I can’t put into words how much I appreciate it!

Typical of the OCR textbook, there are no answers to this part 🙁 This section is found in the summary part, but it is still part of the spec, and there are no answer online either.

Looking at question 3, isn’t a 0.001% increase/decrease of 100 = +- 0.001?
So let’s say the resistor was to increase by 0.001%, R1 would have a resistance equal to 100.001 ohms.

So applying the equation:

V = ((R1/(R1+R2)) – ((R4/(R3+R4)) x 6.0﻿

V = ((100.001/(100.001+100)) – ((100/(100+100)) x 6.0﻿

V = 1.5 x 10^-5 V

Is that right? Or did I go wrong?

• +awesomeoverawesome You’re correct. I didn’t read the question properly!

• +awesomeoverawesome But don’t worry too much about this question – the Wheatstone bridge is not in the OCR spec – it is only an extension task in the book.

• @A Level Physics Online Oh, that is good news! I just assumed it was because it was inside a “green experiment” box. Thank you so much for your help!!! If I manage to somehow get a grade in Physics I will be sure to thank you first; I’m finding it really hard atm.

• Will Vout be more than Vin?

• Nah – V in is being given to the resistors and is being shared between the two. V out is the portion that Resistor 2 gets.

You could connect a load, such as a light, to Resistor 1 as well, then you’ve got 2 V outs (one on R1 one on R2). If you did this and added the voltage value for both V outs, you would get your V in [Kirchov’s second law] 🙂
Its easier to think aboot with a diagram

• is there any video about potentiometer

• Saimakhan Khan
I’m doing the exam tomorrow! :0

• Same 🙁 Good luck!

• Is the output voltage always the same, regardless of what you have in the circuit? Like is it always just the emf for a supply with negligible internal resistance? Or does it increase if you have more resistance in the circuit? Is it just current that varies?

• My physics teacher is pretty shite. So you’re the real MVP. Cheers bruv

• my teacher too is shit. You are better.

• does this still apply if the cell has internal resistance

• Of course it does. Because every cell/battery will have some amount of internal resistance. This equation wouldn’t be very helpful if it only applied to theoretical circuits.

• yes. The resistors are still getting some voltage, even though it’s less than emf. In our scenario here, ” V in” is terminal voltage of cell 🙂

• 3:39 “If you know the current and the resistance at any point in the circuit, you can work out the potential difference across that b*tch”

• THANKS A LOT SIR.

• If R2 changes Vout and V1 both should change, but R1 is fixed, does that mean I changes?

• F

• What happens to the current if the resistance changes

• Excellent explanation!

• In class, I was trying to derive it, couldn’t get anywhere. I come on YouTube and it’s explained by this awesome dude in less than 5 mins

• You are the GOAT 🐐

• That was so simple, you’re really positive aswell, I feel like everything’s going to be okay

• thank you so much you just saved me like 5-6 marks

• Thanks mr matheson, doing this in my AS mocks and this video helped so much – big dad lucas (KS)

• Not a problem

• Ty, this was very helpful. There are a bunch of questions on this in IGCSE physics yet not a single textbook covers this topic

• ❤️❤️❤️❤️

• THANK YOU SIR

• the video is great youre amazing etc etc etc…. but oh my god your intro sound. why. what. stop.

• I have stopped, it’s not there in my videos from the last couple of years

• What a guy ❤️

• Even in 2020 I’m watching these videos and they are so great – thank you so much