The graph below gives the electric potential difference V ac

The graph below gives the electric potential difference V across three different resistors R_1, R_2 and R_3 us a function of the current i in each of the resistors. The solid line refers to resistor R_1, the dotted line refers to resistor R_2, and the dashed line refers to resistor R_3. The scale of the horizontal (current) axis is set by 3.00 mA, and the scale of the vertical (potential difference) axis is set by V_s = 18.0 V. What are the resistances (in Ohms) of the three resistors?

Solution

The slope of the solid line gives the value of the resistance R1

Vs=18 V vertical scale =18/3=6

Is=3 mA= hortizantal scale= 3 mA/3=3 mA

Resistance R1= dV/dI=(18-12)/(3-2)

                                 =6000 ohms

The slope of the dotted line using resistance R2

R2=dV/dI=(12-6)/(3-1.5)

              =4000 ohms

The slope of the dashed line using resistance R3

R3=dV/dI=(6-2)/(3-1)

              =2000 ohms