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Solar Energy- Photovoltaics (solar cells) Photovoltaics • Photovoltaics generate constant electricity– direct current • Electrical terms: – Voltage (difference) (V): Amount of energy per charge required to move charge around a circuit – Current (I): Moving charge • Buildings are powered by alternating current. An inverter is needed to use a photovoltaic to power appliances in the home to convert to alternating current Electric Circuits An electric circuit is often compared to a pipe system Light Intensity And Photovoltaics • Light Intensity: a measure of the energy of the light • The higher the intensity, the more photons generated, hence, greater current and voltage Light wavelength and photovoltaics • • • • Good website on waves Speed of light c= frequency (f)* wavelength (l) c=f l =3 ×108 m/s Frequency f: # of cycles per second that pass a given point Wavelength l : Length of a single cycle of the wave Good website on EM waves Photovoltaics: Amount of current/voltage depends on wavelength • Silicon: Best at infrared wavelengths (l=1mm) Spectral response: he ratio of the current generated by the solar cell to the power incident on the solar cell .