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WHAT IS A DIODE:
A diode lets the current flow in one direction and does not allow the current to flow in the opposite direction.

WHAT DOES IT LOOKS LIKE:
A diode is a two terminal device and is installed in the circuit in the desired manner, so as to let the current flow in the desired direction only. The silvery circle on the diode corresponds to the cathode and the lead connected to black portion is anode.

BARRIER POTENTIAL:
It is a common understanding that whenever positive and negative charges accumulate side by side, there is a potential difference established in between them. And here, in the case of diode, we can see positive and negative charges' layers arranged parallel to each other creating a potential difference known as "barrier potential". Barrier potential is the voltage at the junction due to the accumulation of opposite charges.

The barrier potential for silicon is 0.7 volts while it is 0.3 volts for Germanium.

This means that the battery voltage must be greater than 0.7 volt to overcome the barrier voltage and let the current flow through the diode. 0.7 volts of the voltage supplied by the battery are consumed to eliminate this barrier.

HOW DIODE WORKS:
Diode is nothing more than a simplest p-n junction. Its working is basically its biasing; i.e. how it is connected to the source (battery) in the circuit. There are only two possibilities, a diode can be installed in a circuit. Either it be 'Forward biased' or 'Reverse Biased'.

FORWARD BIAS:
When the anode of the diode is connected with the positive terminal of the battery and the cathode is connected to the negative terminal of the battery, it is said as 'forward biasing' and this is what happens inside: Since diode is a simple p-n junction, few electrons in the portion of p-type(that came during the time of connection of p-type and n-type) are 'sucked' by the positive terminal of the battery creating vacant spaces at the junction. This consequently allows more electrons in the n-type region to cross the junction and enter into those vacant spaces (holes), since the positive terminal of the battery is continuously 'pulling' electrons from the p-type. On the other hand, electrons are being pushed by the negative terminal of the battery into the diode.

So, a constant 'pull' of electrons by the positive terminal of battery from p-type and 'push' of electrons from the negative terminal of the battery into the 'n-type' region (consequently getting into the p-type region through the junction, as the

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