Question

If you were to plot the coulomb’s law formula on a graph , where the slope is equal to kq1q2. Y axis is F and x-axis is 1/r. The equation for the graph is a linear equation where m=slope and b=intercept. What is the meaning/value of this intercept.

Example

Graph : F vs 1/r

y= mx + b

y=(k*2.6x10^-9)x + 2.3x10^-6

Where m=kq1q2 , what would b represent ?

Answer 1

Force F is on y-axis

On x-axis, it should be 1/r² in place of 1/r, then only we can get a straight line graph.

Now,

Intercept b represents that when x= 0, i.e at origin, force between the two charges is 2.3 * 10^-6 N

And

Force between two charges is zero when,

=> 0 = (k*2.6*10^-9)*x + (2.3 * 10^-6)

=> x = -(2.3 * 10^-6) / (k*2.6*10^-9)

         = -(2.3 * 10^-6) / (9*10⁹**2.6*10^-9)

         = -9.83 * 10^-8 m