### Introduction

Energy produced by the sun is called solar energy. It is produced during nuclear reactions that take place throughout the volume of the sun. The energy travels to Earth in the form of light. Photovoltaic (PV) cells, or solar cells, change the light energy to electrical energy that can be used to power calculators, cars or even satellites. A photovoltaic cell is usually made of a semiconducting material such as silicon. When light strikes the cell, it provides enough energy to move electrons through the cell producing an electric current. A single photovoltaic cell is approximately the size of a fingernail and puts out a very small current when struck by the light. Objects requiring higher currents to operate can be powered by wiring large numbers of photovoltaic cells together.

Items powered by solar energy are said to be using solar power. Streetlights that must operate in the dark store the energy in a battery while the sun is shining and then use the energy at night. Scientists working in remote places rely on solar power to operate their computers and equipment. What things can you think of that are powered by solar energy?

In Part I of this experiment, you will measure the current and voltage produced by a photovoltaic cell when exposed to sunlight. You will calculate the power output of the cell using the relationship

$P{\text{ }} = {\text{ }}V{\text{ }}I$ ${\text{Power}} = {\text{voltage}} \times {\text{current}}$

You will also calculate the efficiency of the photovoltaic cell when converting the energy from the sun into electrical energy.

In Part II the relationship between the wavelength of the light striking the photovoltaic cell and power output will be investigated.

### Objectives

In this experiment, you will

• Use a Current Probe to measure current output.
• Use a Voltage Probe to measure voltage output.
• Use a Light Sensor to measure light intensity.
• Calculate power output.
• Calculate efficiency.
• Investigate the relationship between wavelength of light and power output.