Question

The following circuit is used for black/white paper detection in a certain system: 5V Ra R, Va Vout DR 2 Assuming that R3 is fixed, the voltage over the LDR Vais 1V when the LDR is placed over a white paper; and is 2.5V when the LDR is placed over a black paper. Which of the following are possible resistance ratios R:R2 if the desired Vout is 5V when the LDR is placed over a black paper; and Vout becomes 0V when the LDR is placed over a white paper? (1) R:R2 2:3 (2) R:R2 3:2 (3) R1:R2 7:3

Answer 1

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