A fixed system of charges exerts a force of magnitude 21 N on a 6 C charge. The 6 C charge is replaced with a 8 C charge. What is the exact magnitude of the force (in N) exerted by the system of charges on the 8 C charge?

Question

unicorn · Answer

magnitude of electric field will=21/6 N/C

which is because of the fixed system of charge 

and in the second case as only 8C charge is placed in place of 6C charge so the  magnitude of electric field  will remain same 

that means force on 8C charge = 8$$\times$$21/6