Wheatstone Bridge
Introduction to Wheatstone bridge:
Wheatstone bridge is an electric circuit and as the name suggests, it is in a shape of a bridge, the bridge is a galvanometer. It is named after Sir Charles Wheatstone who has popularized this.
Wheatstone bridge helps in finding the unknown resistance value of a resistor. This bridge is also called post office box. We will explain at a latter stage why it is called so.
Let us take a closer look of a Wheatstone bridge.
Description of Wheat stone bridge
The circuit diagram of a Wheatstone bridge is shown above. Four resistors having values of resistances R1, R2, R3, and R4 form sides of a rhombus PQRS and a galvanometer G bridges the points Q and S. A voltage V (usually a DC supply) is applied to the points P and R.
The resistance values R1 and R3, are fixed and are known. R2 is a variable resistance, which is also known. The value is R4 unknown and the Wheatstone bridge principle will help to figure that out.
Principle of Wheatstone bridge:
As mentioned earlier, R2 is a variable resistance. It is varied in such a way that the current reading in the galvanometer shows zero. This is called balancing the Wheatstone bridge. Under this condition,
I1= I2 and I3= I4, since there is no current through the galvanometer.
Also, since there is no current through the galvanometer,
VQP = VSP and VQR = VSR
That is, as per Ohms law,
I3R3 = I1R1
I4R4 = I2R2
Therefore, by division,
`(I_4R_4)/{I_3R_3} = {I_2R_2}/{I_1R_1}`
Since, I1= I2 and I3= I4
`{R_4}/{R_3} = {R_2}/{R_1) `
or, `R4 = R3 {R_2}/{R_1}`
Thus, the value of the unknown resistance can be figured out.
In olden days, in England and in the countries under its regime, the telecommunication was under the control of post offices. When there is a failure in a particular line, it will show an earth resistance proportional to the distance from the post office. The Wheatstone principle used to find that value, in turn, the location of the fault.
This is the reason, in olden days, the Wheatstone bridge was popularly known as post office box.
Looking out for more help on inelastic collisions in physics by visiting listed websites.
Wheatstone bridge is an electric circuit and as the name suggests, it is in a shape of a bridge, the bridge is a galvanometer. It is named after Sir Charles Wheatstone who has popularized this.
Wheatstone bridge helps in finding the unknown resistance value of a resistor. This bridge is also called post office box. We will explain at a latter stage why it is called so.
Let us take a closer look of a Wheatstone bridge.
Description of Wheat stone bridge
The circuit diagram of a Wheatstone bridge is shown above. Four resistors having values of resistances R1, R2, R3, and R4 form sides of a rhombus PQRS and a galvanometer G bridges the points Q and S. A voltage V (usually a DC supply) is applied to the points P and R.
The resistance values R1 and R3, are fixed and are known. R2 is a variable resistance, which is also known. The value is R4 unknown and the Wheatstone bridge principle will help to figure that out.
Principle of Wheatstone bridge:
As mentioned earlier, R2 is a variable resistance. It is varied in such a way that the current reading in the galvanometer shows zero. This is called balancing the Wheatstone bridge. Under this condition,
I1= I2 and I3= I4, since there is no current through the galvanometer.
Also, since there is no current through the galvanometer,
VQP = VSP and VQR = VSR
That is, as per Ohms law,
I3R3 = I1R1
I4R4 = I2R2
Therefore, by division,
`(I_4R_4)/{I_3R_3} = {I_2R_2}/{I_1R_1}`
Since, I1= I2 and I3= I4
`{R_4}/{R_3} = {R_2}/{R_1) `
or, `R4 = R3 {R_2}/{R_1}`
Thus, the value of the unknown resistance can be figured out.
In olden days, in England and in the countries under its regime, the telecommunication was under the control of post offices. When there is a failure in a particular line, it will show an earth resistance proportional to the distance from the post office. The Wheatstone principle used to find that value, in turn, the location of the fault.
This is the reason, in olden days, the Wheatstone bridge was popularly known as post office box.
Looking out for more help on inelastic collisions in physics by visiting listed websites.