CBSE Class 12 Physics 2018 Delhi Set 1 Paper

Question : 20

Total: 26

(a) 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.
(b) Give the truth table and circuit symbol for NAND gate.

Solution:

(a) Drawing the labelled circuit diagram
Explanation of working
(b) Circuit Symbol and
Truth table of NAND gate
(a) 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.
Hence we get a unidirectional/direct current through the load, when the input is alternating current.
(b) The circuit symbol, and the truth table, for the NAND gate, are given below.

Input		Output
A	B	Y
0	0	1
0	1	1
1	0	1
1	1	0

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