A charge of 5C is placed at origin and -10C is placed at the point x= 30 cm. Find the point on the x-axis at which
a) electric field is zero
b) potential is zero.
On electric field and potential
let q1=+ 5 coul and q2 = -10coul
let the resultant field be 0 at some point X from q1.
Remember the electric field is a vector, so while adding it you need to treat the field due to the two charges as vectors taking the direction also into consideration.
Field at any point between the charges will be in the same direction so they cannot add up to zero.
Take a point beyond the two charges, on the line joining the charges. Here the fields due to the charges are in opposite directions. Then total field due to the two charges is zero.
When you are drawing the diagram you have taken the signs of the charges into consideration. Now while solving the question you don't need to use signs of the charges.
9X109 5/X2 + 9X109 ( 10)/ ( 30 + X) = 0
please simpify( solve the equation) this
the value of X is the Point where Electric field is zero
Please follow the same procedure for Potential also potential v= 9X109 q/r
Remember that electric potential is a scalar quantity. So simply add their values and put it equal to zero. You need to consider the sign of the charges while finding the electric potential.
r=x for 5 coul charge and r is 30-x for -10 coul charge.