The 60 -cycle alternating electric current (AC) commonly used in households changes direction 120 times per second. That is, in a one-second time period a terminal at an electric outlet is positive 60 times and negative 60 times. In direct electric current (DC), the flow between terminals is in one direction only. A rectifer is a device that converts alternating to direct current. One type of rectifier is the \(p-n\) junction rectifier. It is commonly incorporated in adapters required to operate electronic devices from ordinary house current. In the operation of this rectifier, a \(p\) -type semiconductor and an \(n\) -type semiconductor are in contact along a boundary, or junction. Each semiconductor is connected to one of the terminals in an AC electrical outlet. Describe how this rectifier works. That is, show that when the semiconductors are connected to the terminals in an AC outlet, half the time a large flow of charge occurs and half the time essentially no charge flows across the \(p-n\) junction.

Step by step solution

01

Understand Functioning of AC

AC or Alternating Current switches polarity 120 times in a second. Each cycle consists of a positive and negative half cycle, implying that each polarity lasts for half the time. Hence, the terminal at an outlet is positive for half the time (1/120 seconds) and negative for the other half.

02

Understand the Role of the Rectifier

A rectifier converts AC to DC. In our case, we're considering a p-n junction rectifier. It consists of a p-type and n-type semiconductor in contact along a junction. Each semiconductor is connected to one of the terminals in an AC electrical outlet.

03

Working Principle of P-N Junction Rectifier

During positive half-cycle, when p-type is connected to the positive terminal and n-type to the negative terminal, the junction barrier gets reduced. This allows current to flow from p-type to n-type. But during negative half-cycle, when n-type is connected to the positive terminal and p-type to the negative terminal, junction barrier gets increased. The resistance during the negative half-cycle is nearly infinite. This is why no current flows in this duration. So, the rectifier allows current to flow only during the positive half-cycles.

04

Conclusion

From steps 2 and 3, it is observed that the current flows half the time across the p-n junction when semiconductors are connected to the terminals in an AC outlet. In the other half, essentially no charge flows. This is how the p-n junction rectifier works, converting AC into DC by clipping off the negative half of the AC current.

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