# April 7 AP Physics. AP Practice Exam April 28 ACT day 1 pm Not optional.

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April 7 AP Physics

AP Practice Exam April 28 ACT day 1 pm Not optional

In: An object of charge +q feels an electric force F E when placed at a particular location in an electric field, E. Therefore, if an object of charge –2q were placed at the same location where the first charge was, it would feel and electric force of a)–F E /2 b)–2F E c)–2qF E d)–2F E /q e)–F E /(2q)

Objective: To learn about static electricity: –Electric field –Electric potential energy –Electric potential –Capacitance –Parallel plate capacitors

Homework check 2, 9, 10, 11

Electric Field

Direction: The direction of the force a positive charge would feel. Strength: The field times the second charge equals the force a second charge would feel.

Electric Field E = F e q o F e = kqq r 2 E = kq r 2

Conducting spheres Electric field is zero everywhere inside the conducting material All excess charge is found on the surface of the material. The electric field just outside the conductor s perpendicular to the surface. Charge accumulates at points

Electric field between two plates Between two plates (except at the edges) the electric field is uniform.

An airplane is flying through a thundercloud at a height of 2 000 m. If there are charge concentrations of +40.0 C at a height of 3 000 m within the cloud and 40.0 C at a height of 1000 m, what is the electric field at the aircraft? at the aircraft?

Electric field lines 1.Lines begin on positive charges and end on negative. 2.The number of lines leaving a positive charge or ending on a negative is proportional the the magnitude of the charge. 3.No lines can cross eachother 4.Lines are perpendicular to the surface of the conductor

Out: The figure shows the electric field lines for two point charges separated by a small distance. (a) Determine the ratio q 1 /q 2. (b) What are the signs of q 1 and q 2 ?

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