♦ It is an arrangement of four resistances used for measuring one of them in terms of the other three. It was devised by Sir Charles F Wheatstone, a British Physicist in 1833.
♦ Wheatstone’s Bridge method is unsuitable for the measurement of very low and very high resistances.
♦ Uses: although the Wheatstone bridge is widely used with manual adjustment for the zero or null galvanometer reading, it is increasingly used with electronic and mechanical arrangements to make it self-balancing, the measurements then being recorded on a paper chart. In this form, the Wheatstone bridge is the basis for many measurement and control devices used in industry. Any quantity such as temperature, humidity, strain, displacement, liquid level in a tank etc. which can be made to produce change in the value of a resistance can be measured with Wheatstone bridge.
♦ Sensitivity: Greater the galvanometer current due to a small deviation from ‘balance’, the more sensitive is the bridge. The sensitivity of the Wheatstone bridge depends upon the following two factors:
(i) Relative magnitudes of the resistances in the four arms of the bridge.
(ii) Relative positions of battery and galvanometer.
Prof. Callender has given the following rule for the greater sensitiveness of the Wheatstone’s bridge.
The battery should be so connected that the resistance in series with the resistance to be measured is greater than the resistance in parallel with it.
Maxwell gave the following rule for best arrangement of resistances constituting Wheatstone’s bridge.
Out of the battery and galvanometer, the one having the higher resistance should be connected between the junction of two highest resistances and the junction of the two lowest resistances.
Reference : Comprehensive Physics, Laxmi Publications
- Principle of A Potentiometer (goforaplusplus.wordpress.com)