Circuits I: Example with Wheatstone Bridge (Unbalanced)

This video works through an example problem where we calculate the current through the middle branch of a Wheatstone Bridge circuit.
University of California, Davis
ENG17: Circuits I, Spring Quarter 2015
Instructor: Dr. Kyle Montgomery
Course Website: www.kmontgomery...

[@saiqohdianah5461]

Thank you so much, Mr. Iam a student from Indonesia and Iam studying for my exam. Wish me luck! :)

[@ThePhDEngineer]

You can do it!

[@glcstln]

Hi, Dr. Montgometry! I found this very helpful. I've a question though, what happens to the equations if, say for example, there's an ammeter in the middle with resistance?

[@sahil1053]

Angeli Grace Castalone that's my question also

[@nabanitagoswami6652]

Apply star delta convertion if unbalanced ...or just remove the registance if the bridge is in balanced condition

[@legallifecons9506]

are you writing backwards? Awesome video.

[@ThePhDEngineer]

+Legal LifeCons I wish I could write backwards! But actually it's just some post-production where we mirror the video feed so that the result is readable. I stand behind a piece of glass with the camera on the opposite side. Glad you enjoyed the video!

[@makanlah6911]

+Dr. Montgomery nice trick I can figure it out and use it for my video awesome !!!

[@JS-gu7fw]

I've been wondering my whole life how youtubers can write backwards. It's so nice of you to give it out. :)

[@kishanl8184]

U guys are dumb

[@succeskiagg3130]

Hiii

[@agustinbugnoni5726]

I liked the video because of the video post production.

[@ThePhDEngineer]

Thanks!

[@asifmuktadir9299]

thanks a lot sir. I found this video on a very crucial moment and it was very helpful

[@chaitanyakeerthi74]

Thats crazy. How is the ink colour flurocent? Can you make a video on how you make videos lol. You need to wear black clothes while shooting the video, the text will be visible then :)

[@soumyajitsarkar2372]

how can we say 6 ohm and 30 ohm are parallel ? Their end is not at the same potential , given a current flows through mid wire .

[@kushagrasonkar]

Exactly my question

[@kushagrasonkar]

I was hoping the current to take the path of least resistance

[@nabanitagoswami6652]

Why not same potential ?..pls explain...I think there is no voltage drop through the wire that's why may be it's in same potential ..am i right?

[@arthurbraganca9564]

U=RI. there's no resistance through the wire, so there's no difference of potential

[@soumyajitsarkar2372]

@@arthurbraganca9564 Well :D, been too long .

[@agathernakiweewa3934]

you are a savior, thank you so much. i needed this to get the whole concept.

[@Eagervul]

Real great video! Thank you very much, I could literally not find this information anywhere else! Not to say it is so well presented!

[@succeskiagg3130]

Hiiii

[@RustedNation]

Thank you very much sir!

[@bekalukassa9308]

Thank you

[@ThePhDEngineer]

You're welcome!

[@cypi11]

yesss sir

[@ThePhDEngineer]

Let's gooooooo!

[@qaiserbozdar1542]

I have a question. I am calculating total resistance by doing series calculations of 6k and 12k and series calculations of 30k and 20k. Then, through parallel calculations of 18k and 50k, the total resistance I achieved was 13.23Kohms. Please explain why this contradiction is happening.

[@doctrina3344]

Broooooo I was so stressed because of school and the happy face at the end made me smile lol

[@ThePhDEngineer]

The happy face cures all...

[@alaattincakir3003]

@Dr. Montgomery According to your video middle points of left and right side have same potential. How can current flow through the wire while there is no potential difference? Could you please explain this contradiction? Thank you..

[@ankitpathak3612]

how to calculate when the bridge has no resistance

[@maxgoris7568]

Thank you sir!

[@ThePhDEngineer]

You're welcome!

[@junnnnzhou4392]

wow this writing screen is so cool

[@donhjoe2162]

How can I calculate the voltage in the section Ix and the section Vx using the redrawing circuit method?

[@sahil1053]

Sir, what would be the current if there is an resistance in path of Id current.and when u upload a video about this if necessary plz send the link in reply......

[@kaziaburousan166]

sir...can you help me in how to calculate equivalent resistance of a unbalanced wheatstone bridge using Nodal Analysis??

[@muhammadjoshua7464]

Kazi Abu Rousan its difficult to calculate the equivalent resistance directly from the diagram, but you can find the total current that flowing in the system with kirchoff rule's first, and from that use V=I.Req to find Req, if you know the potential.

[@muhammadjoshua7464]

Well, actually he already explain it in 3:20.

[@succeskiagg3130]

Hey.......are you from which country????

[@naeemghafori5046]

how we got 122.5 k ohm ?

[@manojkumarsingh51]

Thank you sir for such a suave explanation 🙂🙂

[@ThePhDEngineer]

Most welcome!

[@luhtaubabr2136]

Thanku sir really helpful

[@ThePhDEngineer]

Most welcome

[@trungnguyenchanh5186]

thank you for your explanation; it is very helpful .

[@ThePhDEngineer]

Welcome!

[@emmanuelobaro8298]

thank you sir

[@fazleesulaiman520]

what the voltage of the meter?

[@borntostruggle7595]

Wow!! Thank u sir

[@ThePhDEngineer]

Welcome!

[@anastasiamartinez9526]

Thank you!!!!!!

[@ThePhDEngineer]

You're welcome!

[@pranjalmech8859]

Thank you. Very nicely explained.

[@aneeshsagiraju3985]

Thank u sir , very helpful

[@succeskiagg3130]

Are you from which country

[@ThePhDEngineer]

Welcome!

[@eastern815]

thank you, sir.

[@ThePhDEngineer]

You're welcome!

[@sushi_4life3128]

I'm confused - I thought the definition of a balanced bridge was when there is no potential difference across the bridge thus no current would flow!?

[@ThePhDEngineer]

Yes, a balanced bridge has no current flow through the bridge. That does not have to do with having the same voltage on both sides, which is generally always the case with a current meter placed in the middle. The values of the resistors is all that dictates whether or not current will flow over the bridge.

[@sushi_4life3128]

Right, so am I confusing a very close, but not actually zero potential difference caused by a shortcircuit (the current meter in this case) with an exactly zero potential difference caused by the identical ratio of the series resistors? I = V/R would imply that some voltage and some resistance is necessary for a current.

[@VoidHalo]

I was confused about this too. If there's negligible voltage, there should also be negligible current.

[@marvinschwartz4144]

Don't understand your assumption that the amp meter can be treated as a short. This would mean the voltage on either side of the meter would be the same hence no current flow. Which is what you said in your follow on video for a balanced bridge. Wouldn't it be more correct to show a resistance and either use a delta to y conversion to find the equivalent resistance or use Thevenin's method? Or am I missing something?

[@kartiknair5690]

Thanks a lot sir😄

[@leeong7041]

Thanks sir!

[@Zimmerneo27]

Hello Dr. Montgomery, MD. I realize you made this video with good intentions, however, your best intentions are wrong. If you would like the correct solution to reducing wheatstone bridge resistances, please PM me. I am a 8th grade physics student with a 98 in the class--I know what I am talking about. Thank you. Sincerely, Jack

[@ThePhDEngineer]

Thanks, Jack!

[@akament_shorts]

thanks

[@tmohcin]

thanks

[@dechachumpol4250]

้้้hot หลาย

[@soybeanrice]

Great explanations

[@dechachumpol4250]

167

[@MichaelScarn333]

Great video, thanks a lot

[@hughdominiquegiangodelica5250]

Alex England hjj

[@bosaifcom]

When do we need the Bridge?

[@TheYoungerTroffeys]

Strain gages for load analysis