PhysicsLAB: 2006 Form B

AP Free Response Question
2006 Form B - B3

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Three electric charges are arranged on an x-y coordinate system, as shown above. Express all algebraic answers to the following parts in terms of Q, q, x, d, and fundamental constants.

	(a) On the diagram, draw vectors representing the forces F₁ and F₂ exerted on the +q charge by the +Q and —Q charges, respectively.

	(b) Determine the magnitude and direction of the total electric force on the +q charge.

	(c) Determine the electric field (magnitude and direction) at the position of the +q charge due to the other two charges.

	(d) Calculate the electric potential at the position of the +q charge due to the other two charges.

	(e) Charge +q is now moved along the positive x-axis to a very large distance from the other two charges. The magnitude of the force on the +q charge at this large distance now varies as 1/x³. Explain why this happens.

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