To measure the light intensity the photodiode is used hereinafter. The emf, produced when the light falls on the photodiode, depends in a complex way on the intensity of the incident light. Therefore, the circuit, shown in the figure on the right, is used to measure the light intensity. The voltage measured by a multimeter depends on both the intensity of the incident light and the resistance of the variable resistor.
Install the photodetector and the laser on the optical bench. Direct the light beam exactly at the photodetector. Install a neutral filter in one of the holders. Rotating the laser ring, make sure that the voltage across the resistor (at its maximum resistance) is at least 350 mV.
1.1 Modify the circuit shown above by adding the switch, so that you can measure the resistance of the resistor and the voltage across it with the single multimeter provided. Draw schematically the electric circuit that you propose.
1.2 Using your electric circuit from 1.1, measure the dependence of the voltage across the resistor on its resistance.
1.3 Using the data from 1.2, draw a graph of the voltage across the resistor as a function of its current.
1.4 Draw a graph of the heat power generated in the resistor as a function of its resistance.
1.5 Determine the resistance of the resistor at which the heat power turns maximal. Make additional measurements, if necessary.