Question

A student wants to use two p-n junction diodes to convert alternating current into direct current. Draw the labelled circuit diagram she would use and explain how it works.

Answer 1

Drawing the labelled circuit diagram

Explanation of working

The labelled circuit diagram, for the required circuit is as shown.

The working of this circuit is as follows:

(i) During one half cycle( of the input ac) diode D₁ alone gets forward biased and conducts.

During the other half cycle, it is diode D₂ (alone) that conducts.

(ii) Because of the use of the center tapped transformer the current though the load flows in the same direction in both the half cycles.

Hence we get a unidirectional/ direct current through the load, when the input is alternating current. 

[Alternatively: The student may just use the following diagrams to explain the working.]

Detailed Answer : 

(a) Full Wave Rectifier

Working : For the half cycle of input ac, one of two diode gets forward biased and conducts and output current is obtained across R_L. For –ve half cycle of input ac, the other diode is forward biased and thus output current is obtained due to this diode in this way we get the output current across load R_L for complete cycle of input ac as shown in fig.