WheatStone bridge - Page 1
Forum section: electronics / beginners

author: abdulsamaddabu
author_rank: Contributor
timestamp: August 19, 2018, 11:27:46 am
content: Recently i studied the wheatstone bridge in me physics book in class but i could not understand it properly. I asked the teacher about my confusion but he also dont know. i have posted the picture of topic(wheatstone bridge). My question is ;1.Why current I1 is following through point A to D in loop ADBA.2.Why current I2 is following through point D to C in loop DCBD.My confusion is that why current are following through these two paths. As current always flow through level of a higher potential to a level of lower potential but here it seems opposite.

author: Beamin
author_rank: Super Contributor
timestamp: August 19, 2018, 11:38:09 am
content: That's super hard to read can you take two pictures and turn it right side up? Then I can read it and be as baffled as you are.Cheating:http://www.daycounter.com/Calculators/WheatStone-Bridge/WheatStone-Bridge-Calculator.phtmlWhat I do is put in the values then change one at a time and think about what it's doing as you go up/down or as you approach zero/infinity.

author: abdulsamaddabu
author_rank: Contributor
timestamp: August 19, 2018, 11:51:36 am
content: i have uploaded the pic vertically but i dont know why it is flipped horizontally plz download the pic and flip it backi am very confused about this question

author: DannyTheGhost
author_rank: Contributor
timestamp: August 19, 2018, 12:32:40 pm
content: It's just a model to create equations based on Kirchhoff's rules. During this process you can assume any current direction in loop. Even if you were wrong with direction, the result will show you negative current. in case when there is no actual current, the result of equations will be 0.

author: hsn93
author_rank: Regular Contributor
timestamp: August 19, 2018, 12:41:45 pm
content: i explain it to my self with this phrase:in math, current is a vector number, its just a number + direction.. if you used the negative you are just saying "the direction of (i.e. clockwise) has negative sign.. "flip the thing signs will flip with u.."

author: Brumby
author_rank: Unknown
timestamp: August 19, 2018, 12:45:21 pm
content: How's this:

author: ArthurDent
author_rank: Super Contributor
timestamp: August 19, 2018, 12:48:28 pm
content: I’ve always found it easier to visualize the wheatstone bridge as the redrawn circuit below. Now it consists of 2 resistive voltage dividers (R1/R2 and R3/R4) across a voltage source, Vb. If R1,R2,R3,R4 are all equal then V1 and V2 have to be equal (both Vb/2) and there is no potential difference across the meter so it reads zero center.If R1 and R2 are equal and R4 is a lower value than R3 then V1 is Vb/2 and V2 is less than V1. In this case if you view flow from a higher potential to a lower potential then the flow is from V1 to V2 (blue arrows) and the meter reads to the right. If you now reverse it to have R3 and R4 equal and R2 is a lower value than R1 then V2 is Vb/2 and V1 is less than V2. In this case the flow is from V2 to V1 (red arrows) and the meter reads to the left.This is a very simplistic view of a wheatstone bridge and a commercial bridge will have ratio resistors and sensitivity settings for the actual meter but my basic model still works.

author: Beamin
author_rank: Super Contributor
timestamp: August 19, 2018, 02:18:28 pm
content: You will need one of these to help you:A DMM won't work.Is that text a Pakistani based text? The English is weird.Is the concept you learn when creating the resistor matrix or cube where you can find the values of say a 10X10 matrix or an infinitely big matrix?Nothing better then a 1000 strip of 100resistors, solder, and just make a huge grid then practice ohms law for hours. I think that will solve my "dimbulb" questions.

author: Brumby
author_rank: Unknown
timestamp: August 19, 2018, 04:07:26 pm
content: Quote from: Beamin on August 19, 2018, 02:18:28 pmWhy?

author: Beamin
author_rank: Super Contributor
timestamp: August 19, 2018, 07:00:13 pm
content: Quote from: Brumby on August 19, 2018, 04:07:26 pmI was just being sarcastic at the archaic language used in what looked to be a modern text book. I miss my needle ohm meter sometimes.

author: Brumby
author_rank: Unknown
timestamp: August 20, 2018, 01:41:14 am
content: Being sarcastic in the Beginners section is not wise, IMHO, especially when such posts are not clearly identified as such.It can easily implant wrong ideas into the minds of those who lack knowledge in that area. This can then lead to utter confusion when they try and reconcile this "prior learning" with new information that is inconsistent.We need to be kind andhelpfulto beginners.