A totl charge Q is broken in two parths Q1 and Q2 and they are placed at a distance R from each other the maximum force of repulsion between them will occur when

Dear pallavi

 let parts are sepereted at a distance of d

Q=q1+q2 (conservation of charge)

so repulsion force F= k Q1(Q2)/d²

                                      k Q1(Q-Q1)/d²

     here Q and d are constant so for maximum force differentiate the force w.r.t Q1

 dF/dQ1 = k/d² [Q -2Q1]

 for maximum force dF/dQ1=0

                             Q-2Q1=0

                              Q1 +Q2 -2Q1 =0

                             Q1 =Q2

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