# Chapter 16 Electric Energy and Capacitance

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Chapter 16 Electric Energy and Capacitance
Potential difference and Electric potential Point Charges Charge Conductors Equipotential Surface Capacitance and Capacitors

Work and Potential Energy
How do I calculate work? How do I calculate electric potential energy? How do I relate work with electric potential energy?

Potential Difference What is potential difference?
What are its SI units? Potential difference vs. Potential energy Potential difference for uniform electric field

Example A proton moves a distance of 0.02m parallel to the electric field of 200 N/C. What is the work done by the proton? What is the change in potential energy? What is the change in potential?

Energy and Charge Movements
Basic fact For positive charge For negative charge Energy conservation

Electric Field and Electric Potential of a Point Charge
What is zero electric potential? How do I calculate electric potential due to a point charge? Observations

Electrical Potential Energy of Two Charges
What about Superposition principle? How do I calculate it? What if?

Examples Find the electric potential 1.0 cm from a proton.
What is the potential difference between two points that are 1 and 2 cm apart?

Examples Two point charges are on the y axis, one of magnitude 3x10-9 c at the origin and a second of magnitude 6.0 x 10-9 c at y=30 cm. Find the potential at y=60 cm.

Conductors in Equilibrium
What happens to charge? What about electric field and potential? Electric field Potential

The Electron Volt What is it? What are its units? Some comparisons
Electrons in normal atoms have energies of 10’s of eV Excited electrons have energies of 1000’s of eV High energy gamma rays have energies of millions of eV

Equipotentials and Electric Fields Lines – Positive Charge
What is it? How about work done? How about electric field lines? Dipole

Capacitance What is it? How do I find it? What are its SI units?

Parallel-Plate Capacitor
Construction How does geometry play its part? How does the charge build up on the plates? What does the electric field look like?

Applications of Capacitors – Computers
Computers use capacitors in many ways

Capacitors in Circuits
What is a Circuit? How do you represent a circuit? How do I connect a capacitor in a circuit? What happens when a capacitor is connected in a circuit? What different ways can one connect a capacitor in a circuit?

Capacitors in Parallel
Total charge Potential difference Equivalent capacitance

Equivalent Capacitor How do I calculate equivalent capacitance?

Capacitors in Series How do I connect capacitors in series?
What happens when capacitors are connected in series? The potential difference How do I calculate equivalent capacitance? How do I calculate the energy stored in a capacitor?

Medical Application Defibrillators
When fibrillation occurs, the heart produces a rapid, irregular pattern of beats A fast discharge of electrical energy through the heart can return the organ to its normal beat pattern

Capacitors with Dielectrics
What is a dielectric? How does it affect capacitance? What is dielectric strength? Atomic view of dielectrics

Examples A capacitor of 4 micro farad is connected across the a 12 volt battery. What is the charge on each plate?

Examples Two capacitors are connected in series across a 400 V power source. What is the charge on each capacitor?

Examples Two capacitors are connected in parallel across a 400 V power source. What is the charge on each capacitor?