Photoconductivity

Absorption of light increases electrical conductivity in a solid. In case of cadmium sulphide (CdS) photoresistor, when it is exposed to light the transition of activator electrons into the conduction band and charge exchange of traps with holes being created in the valence band causing enhancement of conductivity.
In the present setup, photo current is studied as a function of the voltage applied to the photo resistor at a constant irradiance. The angle of polarization is changed by polarizer filter.

Features:

• AC/DC power supply with Thermal Safety Switch and safety sockets.
• Multipurpose Power supplies.
• Adjustable Self Centering Slit.
• User friendly design and connections.
• Optical saddles with locking facility and smooth movement.

Objectives:

• To study the current vs voltage characteristics of CdS photoresistor at constant irradiance.
• To measure the photo-current as a function of the irradiance at constant voltage.

Technical Data:

• Photo detector : CdS LDR, Aperture 8-10mm, Mounting rod 10mm dia., 4mm safety terminals, Working voltage 0-20V DC
• Polarizer / Analyzer : Angle (0° ± 90°), Aperture 21mm dia. Frame 130mm dia., Rod 10 mm dia.
• Adjustable Slit : Width 0-2 mm, Height 6 mm, Frame Dia.120 mm to avoids, Mounting rod 10mm dia.
• Light housing : Aluminum, Lamp 12V, 21V, Connection 4mm plug lead, Mounting rod 10mm dia.
• Power Supply : Variable 0-20 Volt DC, Fixed 5V DC and Current 0-1 A (max.), Ripple < 25mV, Overload protection Resettable thermal trip for 5VDC, ON/Off switch with Power Indicator.
• Power Supply : Voltage 2,3,4,5,6,8,10 & 12 V AC full wave, rectified, unsmoothed and unregulated, Overload protection Resettable thermal switch.

Scope of Delivery:

• 1 Photoresistor in holder (CdS)
• 1 Power supply 12V AC/DC 5 Amp.
• 1 Lamp housing 1 Convex lens in holder
• 1 Polarizer/Analyzer (pair)
• 1 Optical bench(1m.)
• 1 Adjustable slit self centering
• 1 Digital multimeter
• 1 Transversal saddle
• 1 Power Supply 0-20V DC, 1A
• 5 Fixed Saddle
• 2 Flexible plug lead, 50 cm (Red)
• 1 Flexible plug lead, 100cm (Black)