A photoresistor, whose resistance decreases with light intensity, is connected i

Question

A photoresistor, whose resistance decreases with light intensity, is connected in the circuit of the figure. On a sunny day, the photoresistor has a resistance of 0.70 k . On a cloudy day, the resistance rises to 4.6 k . At night, the resistance is 27 k . (Figure 1)

What does the voltmeter read on a sunny day?

What does the voltmeter read on a cloudy day?

What does the voltmeter read at night?

Does the voltmeter reading increase or decrease as the light intensity increases?

Does the voltmeter reading increase or decrease as the light intensity increases?

The voltmeter reading decreases because the current through the resistor decreases. The voltmeter reading increases because the current through the resistor decreases. The voltmeter reading decreases because the current through the resistor increases. The voltmeter reading increases because the current through the resistor increases.

Explanation / Answer

part a )

V = IR

R = 1kohm + 0.7 k ohm = 1.7 kohm

I = V/R = 9/1.7*10^3 = 5.29 x 10^-3

Voltmeter reading = V = I*1000 = 5.29 V

part b )

R = 5.6 kohm

I = 1.607 x 10^-3 A

V = I*R2 = 1*1000 = 1.607 V

part c )

R = 28 k ohm

I = V/R = 9/28kohm = 3.21 x 10^-4

V = I*1000 = 0.321 V

part d )

The voltmeter reading increases because the current through the resistor increases.

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