Coupon Accepted Successfully!


Wheatstone bridge

Wheatstone bridge is an arrangement of four resistance which can be used to measure one of them in terms of rest. Here arms AB and BC are called ratio arm and arms AC and BD are called conjugate arms (Fig. 7).
Fig. 7
  • Balanced bridge: The bridge is said to be balanced when deflection in galvanometer is zero, i.e., no current flows through the galvanometer, or in other words VB = VD. In the balanced condition, P/Q = R/S. On mutually changing the position of cell and galvanometer this condition will not change.
  • Unbalanced bridge: If the bridge is not balanced, current will flow from D to B if VD > VB, i.e., (VAVD) < (VAVB) which gives PS > RQ.
  • Applications of Wheatstone bridge: Meter bridge, post office box, and Carey Foster bridge are instruments based on the principle of wheatstone bridge and are used to measure unknown resistance.

Meter bridge

In case of meter bridge, the resistance wire AC is 100 cm long. Varying the position of tapping point B, bridge is balanced. If in balanced position of bridge AB = l, BC = (100 – l), so that
Also 75294.png
⇒ 75303.png
Fig. 8

Test Your Skills Now!
Take a Quiz now
Reviewer Name