Wheatstone Bridge
Wheatstone Bridge is an arrangement of four resistors P, Q, R, and S, such that if we know the value of the resistance of any three of them, we can obtain the value of the fourth unknown resistance by using Kirchhoff's law in balance condition of Wheatstone bridge.
Wheatstone Bridge consists of four resistors P, Q, R, and S in a diamond shape, a voltage source, and a galvanometer to detect the balance condition. Three resistors P, Q, and R are known resistors and the fourth resistor S is an unknown resistor to be measured.
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| Wheatstone Bridge |
✯ Resistors P and Q are in series combination in Wheatstone bridge.
✯ Resistors R and S are in series combination in Wheatstone bridge.
✯ We connect the galvanometer between points B and D.
In loop ABDA by Kirdhhpff's Voltage Law
`I_1 P + I_g R_g - I_2 R = 0` ..... eqn (1)
In loop BCDB by Kirchhoff's Voltage Law
`(I_1 - I_g) Q - (I_2 + I_g) S - I_g R_g = 0` ..... eqn (2)
In the balanced condition of the Wheatstone bridge `I_g = 0` then equations 1 and 2 can be written as
From equation (1)
`I_1 P - I_2 R = 0`
`I_1 P = I_2 R ` ..... eqn (3)
From equation (2)
`(I_1 - 0) Q - (I_2 + 0) S - 0 \times R_g = 0`
`I_1 Q - I_2 S = 0`
`I_1 Q = I_2 S ` ..... eqn (4)
Dividing eq. 3 by eq. 4
`\frac{I_1 P}{I_1 Q} = \frac{I_2 R}{I_2 S}`
`\frac{ P}{ Q} = \frac{ R}{ S}`
This is the equation of a balanced Wheatstone bridge.
Wheatstone Bridge MCQs
Q. What is the primary use of a Wheatstone bridge?
Q. What is the principle behind the operation of a Wheatstone bridge?
Q. Which component in a Wheatstone bridge is adjusted to achieve balance?
Q. When a Wheatstone bridge is balanced, what is the current through the galvanometer?
Q. What is the formula for the balanced condition of a Wheatstone bridge?
Q. Which of the following is not a component of a basic Wheatstone bridge?
Q. In a balanced Wheatstone bridge, if P = 100 `\Omega`, Q = 200 `\Omega` and R = 150 `\Omega`, what is unknown resistance S?
Related Question
1. What is the Wheatstone bridge derivation based on?
2. Draw a Wheatstone bridge diagram"
3. What is the principle behind the Wheatstone Bridge?
4. What formula is used to calculate unknown resistance in a Wheatstone bridge?
5. Who proposed the principle of Wheatstone bridge?
6. Why is the Wheatstone bridge formula important in electrical engineering?
Chapter 3: CURRENT ELECTRICITY
PHYSICS NOTES
- Electric Current Definition and Electric Currents in Conductors
- Ohm’s Law: Definition, Formula, Limitations, Derivation, Diagram, and Deduction of Ohm's Law
- Drift of Electrons and the Origin of Resistivity
- Resistivity, Resistivity of Various Materials, Temperature Dependence of Resistivity
- Mobility Formula in terms of Relaxation Time
- Electrical Energy, Power
- Cells, Emf, Internal Resistance
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