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GATE 2024 IN – Question 32

Sensors and Industrial Instrumentation · Flow and level measurement · 1 mark · Numerical answer

The 0–10 kΩ linear potentiometer shown measures water level. Resistance between A and C changes linearly from 0 to 10 kΩ as water level changes from 0 to 20 cm. The excitation source has $V_s=10$ V and internal resistance $R_s=200$ Ω. If $V_{out}=5$ V, the water level is ______ cm (one decimal place).

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Correct answer: 10.1 to 10.3

Explanation

The potentiometer current is $I=10/(10000+200)$ A. For a 5 V wiper potential, $R_{AC}=5/I=5100$ Ω. Linear scaling gives level $=20(5100/10000)=\boxed{10.2}$ cm.