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Section 3: Electrical Potential Energy and Capacitance. Gravitational vs. Electrical Potential Energy. Voltage or Electrical Potential. Sample Problem: Find the electric potential energy and electric potential .
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Sample Problem: Find the electric potential energy and electric potential
Voltage may also be thought of as “electrical pressure”Voltage always runs for high concentration of electrons to low concentration of electrons
Capacitors: Device that stores charge Activity: Dissecting a capacitor and find out how it stores charge. • Draw a picture of the internal parts of a capacitor. • Use you picture to describe how it works. • One sheet per group.
Parts of a Parallel Plate Capacitor Plates – location where opposite charges are stored 2) Dielectic – Separates the charge and increase the ability to store charge “capacitance”
Design your own capacitor Materials: Aluminum foil and 4 cups Requirements: • Must have electrodes to hook up to. • Must work for full credit otherwise try again Grading: 15 pts • Works and does not arc to itself (15pts) • Works and arcs to self (12 pts) • Does not work (0 pts) keep trying
Capacitor Reflection • Describe how a capacitor works. • Describe how you assembled your capacitor. • What flaws did you find in your capacitor? • List three things you could have done to make your capacitor stronger?
Capacitors and Potential Energy: Capacitance (C): Ability to store charge C = εo A/d εo – permittivity (8.85 x 10-12 C2/N•m2) Charge on Capacitor (Q): Q = CV Potential Energy PEe: PEe = ½(Q)V
Sample Problems • Find the charge on a capacitor that has a capacitance of 2μf ( 2 micro farads) at 30 volts: • If the distance between the plates of a capacitor is .0005m, find its surface area to have one farad of capacitance.
3) Find the potential energy stored in a 5μf capacitor that is charged with 10 volts. 4) Find the surface area charge on the capacitor above.
Activity: Finding the capacitance of a capacitor Procedure: • Charge a capacitor and then discharge it through a resistor (yellow). • Graph current (Coulombs/second) to find the total charge. • Use C = Q/V and compare the value on the capacitor. • Calculate the percent error.