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Questions and Answers
What adjustment is necessary for accurate measurements in bridge circuits?
What adjustment is necessary for accurate measurements in bridge circuits?
- The balance must be exactly zero. (correct)
- The balance must be made equal to the maximum resistance value.
- The balance must vary based on the measurements taken.
- The circuit should have a minimum of two resistors.
Which application is NOT typically associated with the Wheatstone Bridge?
Which application is NOT typically associated with the Wheatstone Bridge?
- Mechanical strain measurements using strain gauges.
- Measuring resistors and resistances.
- Measuring inductance in AC circuits. (correct)
- Low resistance measurements using the Kelvin Bridge.
What is the purpose of a galvanometer in bridge circuits?
What is the purpose of a galvanometer in bridge circuits?
- To provide power to the circuit.
- To amplify the output signal of the bridge.
- To detect the maximum current flow.
- To detect zero current in a circuit. (correct)
What aspect of a measuring instrument is referred to as sensitivity?
What aspect of a measuring instrument is referred to as sensitivity?
In AC bridges, what is the role of impedance?
In AC bridges, what is the role of impedance?
What is the basic principle of a bridge circuit?
What is the basic principle of a bridge circuit?
Which arrangement of components is characteristic of a Wheatstone bridge?
Which arrangement of components is characteristic of a Wheatstone bridge?
What happens when a Wheatstone bridge is balanced?
What happens when a Wheatstone bridge is balanced?
Which equation represents the relationship when a Wheatstone bridge is balanced?
Which equation represents the relationship when a Wheatstone bridge is balanced?
What is a specific modification of the Wheatstone bridge designed for measuring low resistances?
What is a specific modification of the Wheatstone bridge designed for measuring low resistances?
What is one of the key advantages of using bridge circuits?
What is one of the key advantages of using bridge circuits?
What limitation do bridge circuits generally have?
What limitation do bridge circuits generally have?
How does the Wheatstone bridge measure the unknown resistance once it is balanced?
How does the Wheatstone bridge measure the unknown resistance once it is balanced?
Flashcards
Null method
Null method
A measurement technique where an output signal is set to zero to determine an unknown quantity.
Balancing
Balancing
The process of adjusting parameters in a circuit until the output is zero, indicating a balanced state.
Galvanometer
Galvanometer
A sensitive instrument used to detect very small currents in a circuit, crucial for null methods.
Sensitivity
Sensitivity
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Impedance
Impedance
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What is a bridge circuit?
What is a bridge circuit?
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What is a Wheatstone bridge?
What is a Wheatstone bridge?
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What does "balancing the bridge" mean?
What does "balancing the bridge" mean?
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What is the balance equation for a Wheatstone bridge?
What is the balance equation for a Wheatstone bridge?
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What is a Kelvin bridge?
What is a Kelvin bridge?
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What is a strain gauge bridge?
What is a strain gauge bridge?
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What is the advantage of high sensitivity in bridge circuits?
What is the advantage of high sensitivity in bridge circuits?
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What is the advantage of the null deflection method in bridge circuits?
What is the advantage of the null deflection method in bridge circuits?
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Study Notes
Introduction to Bridges
- Bridges are electrical circuits for measuring an unknown electrical parameter by comparison with a known one.
- Common measurements include resistance, inductance, capacitance, and others.
- Balancing the bridge, creating zero current, determines the unknown quantity.
- Different bridge types exist, each tailored for specific applications.
Wheatstone Bridge
- A Wheatstone bridge is a common DC bridge for measuring unknown resistance.
- The circuit has four resistors (R1, R2, R3, Rx) in a diamond shape.
- A voltage source is across opposite corners, and a galvanometer (or null detector) is connected across the other two.
- A balanced bridge has zero potential difference across the galvanometer.
- Balanced condition: R1/R2 = R3/Rx
- This formula calculates unknown resistance (Rx) using known resistances.
- The bridge is highly sensitive to small resistance variations, offering precise measurement.
Types of Wheatstone Bridges
- Variations exist for diverse measurement needs.
- Kelvin Bridge: Designed for precise low resistance measurements, mitigating lead resistance impacts.
- Resistance Strain Gauges Bridges: Measures strain by detecting resistance changes in a mounted strain gauge within the bridge circuit.
Operation of Wheatstone Bridge
- A DC source (e.g., battery) connects to opposite vertices of the bridge.
- A null detector (e.g., galvanometer) connects to the other two.
- Balanced bridge has zero current through the null detector (zero deflection).
- Calibrated adjustments of known resistances achieve the null condition.
- The null point resistance values calculate the unknown resistance.
Advantages of Bridge Circuits
- High sensitivity to small parameter changes.
- Null method yields accurate measurements.
- Simple circuitry for many types
Limitations of Bridge Circuits
- Limited overall accuracy.
- Measurement precision relies on precise known components.
- Precise zero balance is crucial for accuracy; adjustments might be meticulous.
- External factors (e.g., temperature) can affect resistance values.
Applications of Wheatstone Bridge
- Primarily used to measure resistors and resistance values.
- Widely used in mechanical strain measurements with strain gauges.
- Kelvin Bridge variation is crucial for precise low resistance measurements.
Other Types of Bridges
- AC bridges measure inductance (Maxwell, Hay, Anderson) and capacitance (Schering).
- They use AC voltage, employing impedance concepts.
- Balancing method and null detectors apply similarly to AC bridges.
- Different configurations cater to specific frequency ranges.
Key Concepts and Terms
- Null method: Zeroing an output to determine the unknown.
- Balancing: Adjusting parameters to reach zero output.
- Galvanometer: Precision instrument detecting zero current, essential for null methods in bridges.
- Sensitivity: Measuring instrument's ability to detect tiny changes.
- Impedance: Generalized opposition to current flow in AC circuits, encompassing resistance, reactance (inductance and capacitance).
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