Capacitors - a way to store
electric potential energy
How does a cameras flash
unit store energy?
Capacitors are devices that
store electric potential
The energy of a capacitor is
actually stored in the
Any two conductors se
What does the field look like when the disk is very large?
When the disk is very large, it approximates to a uniform
plane sheet of charge.
Uniform plane sheet of charge, E field is independent of
distance from sheet!
Often can appro
Length Vs. Time for a Simple Pendulum
f(x) = 0.2450462114 x^2.0403131853
R = 0.9989405209
Lengt h (m)
T ime (s)
TA Liang Zhang
A and B are
Which is positive?
Which has the
higher E field near
Superposition of electric fields
We use vector addition
Potential energy per unit charge
Units: J/C or Volts
N.B. SCALAR (magnitude, no direction)
Relating work done by electric force to potential
energy and potential
Wa->b here is work done by electric force
(Remember sometimes that
Electric Potential Energy and Potential
We so far looked at
i) electric charge (Q, measured in C)
ii) Force (F, measured in N)
iii) Field (E, measured in N/C)
iv) Flux (! , measured in Nm2/C)
Now, let us introduce electric potential
energy; well denote it
Electric Flux and Gausss Law
Posi6ve charge produces outward electric ux.
Nega6ve charge produces inward electric ux.
Cases with no net charge/ux
What factors impact on the measured ux?