Two positive charges are fixed a distance apart. the sun of their charges is Qt. what charge must each have in order to maximise the electric force between them

Both charges must have the same charge, Qt/2.

Explanation:

Let the two charges have charge Q1 and Q2, respectively.

Use Coulombs's Law to find an expression for the force between the two charges.

, where

Ke is Coulomb's contant and

r is the distance between the charges.

We know from the question that

Q1 + Q2 = Qt

So,

Q2 = Qt - Q1

Simplify to obtain,

In order to find the value of Q1 for which F is the maximum, we will use the optimization technique of calculus.

Differentiate F with respect to Q1,

Equate the differential to 0, to obtain the value of Q1 for which F is the maximum.

It follows that

.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.