A +5.00 μC point charge and -7.00 μC point charge are placed along the x-axis at x = 0.000 cm and x = 40.0 cm, respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net electric force due to the other two charges?

Question

anonymous · Answer

Any position "d" where the force is zero has to fulfill: 5/d^2-7/(d-40)^2=0 and cannot be between the two charges because between the two charges forces ar added whatever the sign of the charge It gives two solutions:d=18.3cm that we can discard for it is between the two charges and d=-218.3 cm that is the valid position

ujjwal · Answer

|dw:1342212592091:dw| The sum of electric fields at the point where charge q is placed is supposed to be zero. Find r (in the figure)