Question

Two identical photoresistors in the dark are connected in series to a constant voltage source. How many times has the resistance of one of them decreased if, when illuminated, the voltage drop across it decreased 2 times?

a) 1 time
b) 2 times
c) 4 times
d) 8 times

Answer 1

When the voltage drop across one of the photoresistors decreases 2 times, the resistance of one of the photoresistors decreases 2 times as well.

Step-by-step explanation:

In this circuit, the two identical photoresistors are connected in series to a constant voltage source. When illuminated, the voltage drop across one of the photoresistors decreases 2 times. We are asked how many times the resistance of one of the photoresistors has decreased.

Let's assume the resistance of one of the photoresistors is R. When the voltage drop across it decreases 2 times, the current through it doubles according to Ohm's law.

The power dissipated by a resistor is given by the formula P = I^2 * R, where I is the current and R is the resistance. If the current doubles, the power dissipated by the resistor increases by a factor of four. Therefore, the correct answer is b) 2 times.