Diodes are made of semiconductors such as silicon and germanium. Application of diode can be realised from the circuit which consists of power supply ,diode and resistor. Now multimeter settings are kept in low DC voltage setting and power is switched on.
The flow of current through resistor can be calculated by Ohm's law I = V /R. Assuming above set up as mathematical model, two things can be revealed. Diode acts as a switch and the load is only across the resistor.
High resistance property of diodes while it is reverse biased can be found by multimeter in Ohm setting. The positive end (red wire) of multimeter is connected to anode of a diode and negative end (black wire) to cathode of diode. Multimeter reading shows low resistance of diode. If connection is made such that positive end to cahode and negative end to anode, meter shows high resistance.
Self activated switching function of diodes can be known by a diode connected with battery and lamp.Battery or power source of 6 V is taken and positive end of battery is connected to anode of diode and negative end of battery is connected to cathode of diode through a lamp. Now voltage across diode is measured by multimeter and it shows 0.7 V because it is the voltage needed for diode to forward bias. The voltage across lamp shows that 5.3 V and it glows.On other experiment, the diode is reverse biased by changing its terminals.The multimeter readings are taken by putting it across diode. It is noted that 6 V and the lamp does not glow since the voltage across the lamp is zero.
Diodes are extensively used in many applications. Diodes are utilized for changing AC current to DC current (Rectifiers), functioning as a switch and preventing voltage spikes. In digital circuits , functions of logic gates can be exhibited using diodes. Further, diodes are used in clipper and clamper circuits. Light emitting diode (LED), a type of diode , is used as a sensor. Zener diode,tunnel diode and laser diode are some of the type of diodes and they are largely used in practical application.