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Wheatstone Bridge MCQs are important questions from the Current Electricity concept from the latest CBSE Class 12 Physics Syllabus. Wheatstone Bridge MCQs cover concepts related to the components of the bridge circuit, its measurement, and its effects on other electrical components.
Wheatstone Bridge works on the principle of zero deflection. It is used to measure the unknown resistance in an electrical circuit. The Wheatstone bridge was discovered by Samuel Hunter Christie in 1833. Wheatstone Bridge is a resistance bridge that comprises 2 unknown resistors. One of these legs is an unknown resistor and the other is a variable resistor. These two when connected as a bridge give a reliable and accurate measurement.
Wheatstone Bridge Setup
The basic principle involves measuring the ratio of the resistances which are equal such that there is no current flow through the electrical circuit. The bridge is unbalanced under normal conditions and hence current flows through the galvanometer. This flow is achieved by balancing the known and the variable resistances.
Read More: NCERT Solutions for Class 12 Physics Chapter 3: Current Electricity
Class 12 Wheatstone Bridge MCQs
Ques. Electric Strain Gauges are measured by a Wheatstone bridge because
- High Sensitivity
- Low Sensitivity
- Sensitivity is Zero
- Sensitivity has a finite value
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Ans. The correct option is B. High Sensitivity.
Explanation: The characteristic features of the Wheatstone bridge are:
- Consists of two resistances in a series and parallel arrangement.
- Resistances are connected between a voltage supply and ground, thereby producing net zero voltage in the two legs at balanced conditions
- Wheatstone bridge measures medium resistance and should not be used for low resistance measurements as an error is produced.
- The high sensitivity of the Wheatstone bridges makes it applicable in electric strain gauges.
- There are two input and output terminals each with four resistors connected in a diamond-shaped arrangement.
- At balanced condition, \(\frac{R_1}{R_3}=\frac{R_2}{R_4}\)
Ques. Wheatstone bridge is a __________
- A.C. bridge
- High voltage bridge
- Power Dissipation bridge
- D.C. bridge
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Ans. The correct option is D. D.C.Bridge.
Explanation: Medium resistance is measured by Wheatstone bridge which is a D.C. Bridge. High voltages are measured using Schering Bridge. Ac bridges comprise Anderson and Maxwell Bridges.
Ques. Why is D.C resistance for different wires measured using a Wheatstone bridge?
- To maintain a source of constant e.m.f
- To calculate the effective resistance
- Check the quality of wire
- To calculate the power dissipated
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Ans. The correct option is C. Check the quality of the wire.
Explanation: In the Wheatstone bridge circuit the source of voltage remains the same and this maintains a constant e.m.f in the circuit. This is why D.C. resistance is measured in different wire materials to check their quality.
Ques. The resistance range measured by the Wheatstone bridge is?
- 10kΩ to a few megaohms
- 100Ω to a few teraohms
- 1Ω to a few megaohms
- 100MΩ to a few gigaohms
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Ans. The correct option is C. 1Ω to a few megaohms.
Explanation: Wheatstone bridge is typically employed to measure medium resistance and not lower resistance ranges. Thus the measurement range varies from 1Ω to a few megaohms.
Do Check Out:
| Important Topics from Class 12 Chapter 3 Current Electricity | ||
|---|---|---|
| Ohm’s Law | Cells in Series & Parallel | Resistor Applications |
| Carbon Resistor | Power and Resistance | Potentiometer |
| Voltage Divider Formula | Static Electricity | Current Density Formula |
| Internal Resistance | Network Analysis | Resistance and Length Formula |
Ques. What is the cost of maintenance of a Wheatstone Bridge?
- Expensive
- Low
- Source e.m.f dependant
- Component dependant
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Ans. The correct option is A. Expensive.
Explanation: The maintenance cost of a Wheatstone bridge is extremely high owing to its resistance tolerance limit of up to 1%. The source of voltage or the components do not add up to the expenses as there are typically uniform for all bridge circuits.
Ques. The effect of galvanometer in measuring high resistance is_____________
- Dependant on the source e.m.f.
- It becomes insensitive to imbalances in the circuit
- Zero
- Dependant on the galvanometer type
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Ans. The correct option is B. It becomes insensitive to imbalances in the circuit.
Explanation: When high resistance is measured using a Wheatstone bridge, the galvanometer can't sense such high resistance values and fails to detect an imbalance in the circuit.
Ques. What does the following figure indicate about the circuit?
- It is a high resistance construction
- It is a medium resistance construction
- It is a low resistance construction
- It is an extremely low resistance construction
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Ans. The correct option is C. It is a low-resistance construction.
Explanation:
The ammeter A measures the current passing through the electric circuit. The voltmeter V measures the voltage. Thus, the above construction is meant for low resistances.
Ques. _________ is not a source of error in the low resistance measurement.
- The thermal e.m.f
- The effect of temperature
- The power dissipated through the electrical circuit
- The drop in contact resistance at the leads
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Ans. The correct option is A. The thermal e.m.f
Explanation: The current flowing through a low resistance circuit is always low. This causes a drop in voltage across the terminals thereby nullifying the contact and lead resistances. The high current flow induces a temperature increase causing a thermal e.m.f. to occur.
Ques. What are the terminals aa’ used for?
- To measure the power dissipation of circuit
- To measure the current flow through circuit
- To measure the voltage drop across the resistance
- To measure the resistance of circuit
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Ans. The correct option is C. To measure the voltage drop across the resistance
Explanation: The voltmeter V is connected across the terminals aa’. This measures the voltage drop across the resistance R.
Ques. What is the value of the current I?
- I = Iv Ir
- I = Iv ⁄ Ir
- I = Iv + Ir
- I = Iv – Ir
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Ans. The correct option is C. I = Iv + Ir
Explanation: At node N, Kirchhoff’s current law is applied
I = Iv + Ir
where,
I is the total series current flowing through the circuit
Iv is the current flowing through the voltmeter
Ir is the current flowing through the resistance R
Ques. If the source and the detector are interchanged in a Wheat stone bridge, then the balance condition becomes?
- Reduced to half
- Independent of the source or detector type
- Remains the same
- More by a factor of 2
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Ans.The correct option is B. Independent of the source or detector type
Explanation: In a Wheatstone bridge, balancing occurs with the help of the output signal from the detector being balanced automatically or manually. This happens in the form of a feedback loop which then finds the null position. The unknown resistance under the balancing condition Rx is
Rx = (R3R1)/R2
This state is not dependent on the source resistance of the voltage source or the sensitivity or the input resistance of the detector.
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