Physics
Ch. 18-1 (Pages 666-669)
I. Electrical Energy & Electric Force
-Electrical potential energy –
 Results from interactions of 2 objects’ _______________
- ΔPE electric  change in electric potential energy (final minus initial)
- Factors determining PE electric
1.
2.
3.
- Electrical potential energy in a uniform electric field
PE electric= -q E d  displacement from ref. point

Charge electric field strength
(Single charge)
- Electric potential energy for a pair of charges
PE electric= Kc (q1q 2)
R
Kc=8.99 x 109 N(m2/C2)
(Coulomb constant)
-Reference point assumed to be infinity
18-2 Potential difference (p.670-675)
-Electric potential-electric potential energy of a charged particle in an electric field
(divided by its charge)
Electric potential (V) = electric potential energy
charge of the particle
V = PE electric
q
- V is measured in ____________1 _____________ = 1
-__________________ ________________- change in electrical potential energy (V)
*only changes in electric potential are significant and important
ΔV = PE electric
q
 ΔV Measured in volts (V) = 1 Joules/Coulomb
- ΔV measures the change in _______________ per unit of ________________
- A potential difference within a battery causes ____________________ to move
- ex.  12 Volt car battery
- positive terminal has electric potential of 12 V
- negative terminal has electric potential of 0 V
- Positive terminal has a higher electric potential then the negative terminal
- As 1 coulomb of charge moves from negative to the positive terminal the battery does work
on the charge to increase the PE electric of the charge to 12 J of electric potential energy
- Each coulomb of charge that leaves the battery would have 12 J of energy
- This energy is given up to the parts of the device which is run from the battery
18-3 Capacitance
______________________ - a device used in electrical circuits as a storehouse of charge
- Stores positive and negative charges ___________________
-Parallel-plate capacitor - two metal plates separated by a small distance
- Connected to the 2 terminals of a battery (once charged, battery removed)
- Charge is removed from one plate and accumulates on another
-Capacitance- the ability of a conductor to store ____________ in the form of electrically
separated ________________
 Ratio of net charge on each plate to potential difference
- SI unit is the __________________ (F) =
- Capacitance depends on the _________, ___________, and ____________ of the capacitor
- Larger plates = ____________storage of energy
- Materials between plates can change capacitance
- Charged capacitors release energy ____________
 Ex. – camera flash, computer keyboard
- Capacitance
C=Q
ΔV
Capaticance = Magnitude of charge on each plate
Potential difference