Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): When the voltage across a diode is reversed, keeping its size the same, the current has the same size as before but flows the other way.
Reason (R): Materials and devices that do not obey Ohm’s law are widely used in electronic circuits.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) is not correct but (R) is correct.
Assertion (A) When the voltage across a diode is reversed, keeping its size the same, the current has the same size as before but flows the other way. — False. For a diode the relation between \( V \) and \( I \) depends on the sign of \( V \). When \( V \) is reversed, the current in the opposite direction is not of the same size as before. This is one of the ways in which a device fails to follow Ohm’s law.
Reason (R) Materials and devices that do not obey Ohm’s law are widely used in electronic circuits. — True. Devices such as the diode do not follow Ohm’s law, yet they are used in electronic circuits all the time.
NCERT (2026-27):
Limitations of Ohm’s Law – “(b) The relation between V and I depends on the sign of V. In other words, if I is the current for a certain V, then reversing the direction of V keeping its magnitude fixed, does not produce a current of the same magnitude as I in the opposite direction … This happens, for example, in a diode which we will study in Chapter 14.”
Limitations of Ohm’s Law – “Materials and devices not obeying Ohm’s law … are actually widely used in electronic circuits.”