Current-voltage characteristics of two elements A and B are as shown below in Figs. (a) and (b).
(a)
Which of the following graphs represents current voltage characteristics for their series combinations ?

Options

A.
B.
C.
D.

Answer

C

Explanation

In the voltage does not increase this current (which is constant at 1 A). This means that the ratio. `V//R_(A)` = constant and this resistance `R_(A)` increases linearly with voltage
In element B, the resistance decreases gradually upto 15 V and afterwards the resistance Re increases linearly with voltage.
When both A and B are in series, the current in the circuit will increase non-linearly upto 1 A when the total voltage drop across A and B becomes `10 + 15 = 25 V` Further increase in this voltage does not bring about any change in the current as shown in solution (C). The voltage drop across A will go on increasing while that across B remains fixed at 15 V. Hence (C) is correct