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State working principle of potentiometer. Explain how the balance point shifts when value of resistor R increases in the circuit of potentiometer, given below. |
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Answer» Solution :A potentiometer WORKS on the principle that for a constant current flowing through the potenti-ometer wire of uniform cross-section the fall in potential is directly proportional to the length. When value of resistor R is increased in the circuit of potentiometer, current flowing through potentiometer wire due to driver CELL V decreases and consequently the valueof potential gradient .k.along potentiometer decreases. Mathematically `I=(epsilon)/(R+R_(1))`, where `epsilon=emf` of driver cell and `R_(1)=` resistance of potentiometer wire and `k=1(R_(1))/(L)`, where L = TOTAL length of potentiometer wire AB. `rArr""k=(epsilon R_(1))/((R+R_(1))L)` Due to decrease in the value of .k., the BALANCE point will shift towards right i.e., the BALANCING length increases. |
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