Metre Bridge Experiment Viva Questions
Metre Bridge Experiment Viva Questions (FAQ) – CBSE Physics Practical
This post provides a complete and exam-oriented collection of viva questions for the metre bridge experiment. These questions are frequently asked in CBSE physics practical examinations while performing the experiment to find the resistance of a given wire using a metre bridge.
Experiment: To find resistance of a given wire / standard resistor using metre bridge
Basic Viva Questions on Metre Bridge Experiment
Q1. What is a metre bridge?
A metre bridge is a practical form of Wheatstone bridge used to measure unknown resistance.
Q2. What is the principle of a metre bridge?
It works on the principle of Wheatstone bridge.
Q3. Why is the bridge wire one metre long?
Because resistance is proportional to length and a one-metre wire allows direct comparison.
Q4. What is the null point?
The point on the wire where the galvanometer shows zero deflection.
Q5. Which instrument is used to detect the null point?
Galvanometer.
Procedure-Related Viva Questions
Q6. How is the circuit arranged in a metre bridge experiment?
The unknown resistance and known resistance are placed in the two gaps of the metre bridge and connected with a battery, key, galvanometer, and jockey.
Q7. Why should the jockey be touched lightly on the wire?
Pressing hard may change the resistance of the wire.
Q8. Why are the resistances interchanged during the experiment?
To minimize end error and improve accuracy.
Q9. Why is the key inserted only while taking readings?
To prevent heating of the wire.
Q10. Why should the balance point not be near the ends of the wire?
Because end resistances introduce large errors.
Conceptual Viva Questions
Q11. Write the formula used in metre bridge experiment.
\[
\frac{X}{R} = \frac{l}{100 – l}
\]
Where:
(X) = unknown resistance
(R) = known resistance
(l) = balancing length
Q12. Why must the bridge wire be uniform?
So that resistance is directly proportional to length.
Q13. What happens if the wire is non-uniform?
The result becomes inaccurate.
Q14. Why is a low-resistance galvanometer preferred?
For better sensitivity and accurate null detection.
Q15. What physical quantity becomes equal at the balance point?
Potential difference across the two arms of the bridge.
Application-Based Metre Bridge Viva Questions
Q16. Where is the metre bridge principle used?
In electrical testing and resistance measurement.
Q17. Can metre bridge be used to measure very high resistance?
No, it is suitable only for moderate resistances.
Q18. How is this experiment useful in finding resistivity?
By combining resistance with length and cross-sectional area.
Q19. What is the effect of temperature rise during the experiment?
Resistance increases, causing error.
Q20. Can two unknown resistances be compared using metre bridge?
Yes.
Error Analysis (Types of Errors)
Q21. What types of errors occur in a metre bridge experiment?
Systematic errors, random errors, and observational errors.
Q22. What is systematic error in a metre bridge experiment?
A consistent error caused by end resistance of copper strips, connecting wires, or non-uniform bridge wire.
Q23. What is end error in a metre bridge?
End error is a systematic error due to resistance of copper strips and connecting wires at the ends of the bridge.
Q24. How can end error be minimized?
By interchanging the known and unknown resistances and taking the mean of the readings.
Q25. What are random errors in a metre bridge experiment?
Errors caused by small fluctuations in jockey position, galvanometer sensitivity, or external disturbances.
Q26. What are observational errors in this experiment?
Errors due to incorrect reading of balancing length or parallax error while observing the scale.
Q27. How does heating of the wire cause error?
Heating increases the resistance of the wire, leading to incorrect balancing length.
Q28. Why is the balance point preferred near the middle of the wire?
It reduces percentage error in length measurement and minimizes end error.
Q29. What precaution helps reduce contact resistance error?
Ensuring clean connections and touching the jockey lightly on the wire.
Q30. How does zero error of the metre scale affect the result?
Zero error introduces a systematic shift in the measured balancing length, affecting the calculated resistance.
Quick Examiner-Style Viva Questions
- SI unit of resistance: Ohm (Ω)
- If balancing length is 50 cm: Both resistances are equal
- Why copper strips are thick: To make resistance negligible
- Why plug key is used: To control current flow
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