Using Potentiometer to find balancing emf.

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    Emf Potentiometer
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SUMMARY

The discussion centers on the use of a potentiometer to balance the electromotive force (emf) of a secondary cell. It is established that connecting a high resistance in series does not affect the null point when measured with a potentiometer, as there is no current flowing through the resistor at balance, resulting in no voltage drop. The potential gradient of the potentiometer is significantly greater than the potential drop caused by the high resistance, allowing for accurate measurements without the resistor. This understanding clarifies the relationship between resistance and effective balancing length in potentiometric measurements.

PREREQUISITES
  • Understanding of potentiometer principles
  • Knowledge of electromotive force (emf) concepts
  • Familiarity with circuit theory and resistance
  • Basic knowledge of voltage measurement techniques
NEXT STEPS
  • Study the principles of potentiometer circuit design
  • Learn about the effects of resistance on circuit behavior
  • Explore the concept of potential gradient in electrical circuits
  • Investigate practical applications of potentiometers in measuring emf
USEFUL FOR

Electronics students, physics educators, and engineers involved in circuit design and measurement techniques will benefit from this discussion, particularly those interested in the practical applications of potentiometers in balancing emf.

harjyot
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According to my book, if we connect a high resistance in series to the secondary cell (whose emf is to be balanced) , connect this whole apparatus to a potentiometer with an auxiliary Emf and find the null point . It's written that even after removing the Hugh resistance the null point comes down to be the same. How's that ? Doesn't the High resistance In fact contribute to increase the effective balancing length? Or do we assume that the potential gradient of the potentiometer far exceeds the potential drop created by the resistance?
 
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I would have been nice to have a circuit showing what you mean. My guess is that when in balance there is no voltage drop across the "high resistance". So no current flowing through it which means it can be replaced with a short circuit without anything changing.
 
harjyot said:
According to my book, if we connect a high resistance in series to the secondary cell (whose emf is to be balanced) , connect this whole apparatus to a potentiometer with an auxiliary Emf and find the null point . It's written that even after removing the Hugh resistance the null point comes down to be the same. How's that ? Doesn't the High resistance In fact contribute to increase the effective balancing length? Or do we assume that the potential gradient of the potentiometer far exceeds the potential drop created by the resistance?

When the potentiometer is balanced, there is no current through the series 'protection' resistor so there is no voltage drop across it and the reference cell voltage also appears on the slider of the pot.
 

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