AP Practice Exam April 28 ACT day 1 pm Not optional
In: Two 1 kg spheres each carry a charge of magnitude 1C. How does F E, the strength of the electric force between the spheres, compare to F G, the strength of their gravitational attraction? a)F E < F G b)F E =F G c)F E >F G d)If the charges on the spheres are of the same sign, then F E >F G ; but if the charges on the spheres are of the opposite sign, then F E <F G e)Cannot be determined without knowing the distance between the spheres.
Objective: To learn about static electricity: –Millikan Oil Drop Experiment –Electric potential energy –Electric potential –Capacitance –Parallel plate capacitors
Electric potential energy The work done to bring a charge from infinity to a particular distance = - potential energy the charge has at that point. U E =-Work Also, the change in PE from one point to another = -work done to change the position. ΔU E =-W
In a field generated by a point charge: U E =kq 1 q 2 r In a uniform field: ΔU E =qEΔd
Both Gravitational potential and Electrical potential energy depend on position
Electric potential The energy per each individual charge. Measured in Volts V = U E q