Question

In the given figure, which of the diodes are forward biased?

A. 1,2,3
B. 2,4
C. 1,3,4
D. 2,3,4

Answer 1

The above figures are the examples of p-n junction diodes. A p-n junction diode is a special heavily doped diode that allows the electric current to flow in one direction. When the p-n junction diode will be forward biased, the p-type will be connected to the positive terminal and n-type will be connected to the negative terminal.

Complete answer:
In figure 1 , the n-type is connected to +5V (positive terminal) and p-type is connected to earth (negative terminal). This means that the barrier potential of the n-terminal will be higher than the p-terminal. Therefore, it is reverse biased.

In figure 2 , the p-type is connected to 10V and the n-type is connected to . therefore, it will be forward biased and its voltage will be +5V .In figure 3 also, the barrier potential of n-terminal is greater than the p-terminal. Hence, it is reverse biased.

In figure 4 , the n-type is connected to -12V and the p-type is connected to -5V . This means that the potential of p-terminal is higher than the n-terminal. Therefore, it is forward biased.In figure 5, again the potential of n-terminal is greater than the p-terminal, hence, it is reverse biased.

Therefore, we can say that, in the given figure the diodes that are forward biased are 2 ,4.Hence, option B is the correct option.

Note: When we say that the p-n junction is forward biased, this means that current can flow through it. On the other hand, when the p-n junction is reverse biased, the current will not flow through it. Also, when the potential of n-type will be greater than the p-type, p-n junction will be reverse biased. When the potential of n-type will be lower than the p-type, p-n junction will be forward biased.