Chapter 16
Electric Energy andCapacitance
1. Potential difference and Electric potential2. Point Charges3. Charge Conductors4. Equipotential Surface5. 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.
a) What is the work done by the proton?
b) What is the change in potential energy?
c) 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?
Examplesa) Find the electric potential 1.0 cm from
a proton.b) What is the potential difference
between two points that are 1 and 2 cm apart?
Examplesa) 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?
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