What is a Wheatstone bridge and how is it used for resistance measurement?
1 Answer
A Wheatstone bridge is a circuit used to measure an unknown electrical resistance by comparing it with a known resistance. It was invented by Samuel Hunter Christie in 1833 and later popularized by Sir Charles Wheatstone in 1843, hence its name.
The Wheatstone bridge consists of four resistors connected in a diamond-shaped arrangement. The basic components of the bridge are:
Unknown resistor (Rx): The resistance value of the component you want to measure.
Three known resistors (R1, R2, and R3): These are resistors with precisely known resistance values.
The circuit is set up with a voltage source connected across one diagonal of the diamond, and a galvanometer (a sensitive current-measuring device) is connected across the other diagonal. The bridge is then balanced when the ratio of the resistances on one diagonal is equal to the ratio on the other diagonal. In a balanced condition, the current through the galvanometer becomes zero.
The balance equation for the Wheatstone bridge is given by:
Rx/R2 = R1/R3
By rearranging the equation, you can calculate the value of the unknown resistor (Rx):
Rx = (R1 * R2) / R3
To measure the unknown resistor, you vary the value of one of the known resistors (R1, R2, or R3) until the galvanometer shows zero deflection. At that point, the bridge is balanced, and you can then calculate the value of the unknown resistance (Rx) using the equation mentioned above.
Wheatstone bridges are commonly used in electrical and electronic circuits for measuring resistance with high precision. They can be used in various applications, including measuring the resistance of strain gauges, thermistors, and other sensors. However, it's worth noting that Wheatstone bridges are most effective when the resistances involved are within the same order of magnitude. For very high or very low resistances, other methods or specialized bridge configurations may be more suitable.
The Wheatstone bridge consists of four resistors connected in a diamond-shaped arrangement. The basic components of the bridge are:
Unknown resistor (Rx): The resistance value of the component you want to measure.
Three known resistors (R1, R2, and R3): These are resistors with precisely known resistance values.
The circuit is set up with a voltage source connected across one diagonal of the diamond, and a galvanometer (a sensitive current-measuring device) is connected across the other diagonal. The bridge is then balanced when the ratio of the resistances on one diagonal is equal to the ratio on the other diagonal. In a balanced condition, the current through the galvanometer becomes zero.
The balance equation for the Wheatstone bridge is given by:
Rx/R2 = R1/R3
By rearranging the equation, you can calculate the value of the unknown resistor (Rx):
Rx = (R1 * R2) / R3
To measure the unknown resistor, you vary the value of one of the known resistors (R1, R2, or R3) until the galvanometer shows zero deflection. At that point, the bridge is balanced, and you can then calculate the value of the unknown resistance (Rx) using the equation mentioned above.
Wheatstone bridges are commonly used in electrical and electronic circuits for measuring resistance with high precision. They can be used in various applications, including measuring the resistance of strain gauges, thermistors, and other sensors. However, it's worth noting that Wheatstone bridges are most effective when the resistances involved are within the same order of magnitude. For very high or very low resistances, other methods or specialized bridge configurations may be more suitable.