Wheatstone Bridge Principle states the if four resistance P, Q,
R and S are arranged to form a bridge as shown in figure with a cell E and one
key K1 between the point A and C and galvanometer G and tapping key K

_{2}between the points B and D, closing K_{1}first and K_{2}later on, if the galvanometer shows no deflection then bridge is balanced.
Current distribution in the circuit is shown in the figure. Total
current by cell is I, it distributed to P and S as I

_{1}and I-I_{1}. Let current through galvanometer is*I*_{g}.
Current in Q is

**and in S current are***I*_{1}-I_{g}**Resistance of galvanometer is G.***I-I*_{1}+I_{g}.
Now apply Kirchhoff’s 2nd law in ABDA, we get

*I*_{1}P +I_{g }G – (I-I_{1}) R=0*…..…1*

Now apply Kirchhoff’s 2nd law in BCDB, we get

*(I*_{1}–I_{g}) Q – (I-I_{1}+I_{g}) S – Ig G = 0**…….2**

If value of R is such that the galvanometer shows no deflection
that is

**. Putting this value in equation 1 and 2 we get***I*_{g}= 0
This last equation relating the four resistors is
called the

**balance condition for the galvanometer**to give zero or null deflection.
A practical device using this
principle is called the

**meter bridge**.
sir, your notes are still helping. i am doing aerospace engineering from amity university. URVASHI PUNDIR

ReplyDeleteoohh...that is really very nice ....Aerospace Engineering was my dream.....good...keep doing good work.

DeleteRegards

DMR

Sir, could you explain How is the Wheatstone principle used in a meter bridge to find out an unknown resistance? Your notes were very helpful though. I'm doing 10th Grade CBSE. Please help ASAP. :)

ReplyDeleteHi Mohit,

DeletePlease refer this link:

http://dmr-physicsnotes.blogspot.in/2013/01/slide-wire-bridge-or-meter-bridge.html

Regards

DMR

Thank you sir

ReplyDeleteWheastone Bridge, app for calculation of the Rx resistance of a Wheatstone bridge

ReplyDeletehttps://play.google.com/store/apps/details?id=com.fjapps.juank.classwheastone&hl=en

Sir u r too good at teaching by the looks of it ����

ReplyDeleteSir could you tell me all the names of important deeivations of class 12 physics plz

ReplyDelete