A linear resistance potentiometer is 50 mm long and is uniformly wound with a wire of total resistance 5000 ohm. Under normal conditions, the slider is at the centre of the potentiometer. Determine linear displacement when the resistance of the pot, as measured by the Wheatstone bridge is 1850 ohm. If it is possible to measure the value of 5 ohm resistance with the above arrangement, determine the resolution of pot in mm.
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4.5 mm and 0.5 mm
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6.5 mm and 0.05 mm
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65 km and 0.05 mm
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6.5 mm and 0.005 mm
B
Correct answer
Explanation
Total resistance of the pot wire (Rt) = 5000 ohm
Total length of the pot wire (L) = 50 mm
Resistance per mm length of pot wire (Rt/L) = 5000/50 = 100 ohm
Resistance of pot at normal position = 5000/2 = 2500 ohm
Change in resistance of pot from its normal position = 2500 – 1850 = 650 ohm
Dispalcement (y) = 650/100 = 6.5 mm
Minimum measurable value of resistance = 5 ohm
Resolution of pot = Minimum measurable resistance/Resistance per mm length = 5/100 = 0.05 mm 6.5 mm and 0.05 mm