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REVIEW SHEET
STATIC AND DYNAMIC ELECTRICITY
1. COULOMB’S LAW: Formula for calculating the force between two point charges. Force repulsive if
both charges are the same sign, attractive if they are different signs
F
kq1q2
r2
k = Coulomb constant = 9 x 109 Nm2/C2
q1 - charge on the first point
q2 - charge on the second point charge
r - distance between the charges
2. ELECTRIC FORCE:
F  qE
q - magnitude of the charge
E - Electric field strength
3. WORK DONE (Electric Energy): In moving a charge in an electric field:
4. VOLTAGE AND WORK (Electric Energy):
V
W
q
W – Work (Energy)
V- Voltage (potential difference)
q - charge
Work =
Joules
eV’s
W  qV
Charge x
Coulombs
Elementary
charges
Voltage
Volts
Volts
5. ELEMENTARY CHARGE:
a. qe - charge on an electron = - 1.6 x 10 -19 coulombs (fundamental unit of charge)
b. qp - charge on a proton = 1.6 x 10-19 coulombs (fundamental unit of charge)
c. Like a penny - no smaller coin - charge cannot exist in a smaller unit.
d. 1 Coulomb = 6.25 x 1025 elementary charges
6. TOTAL CHARGE:
a. Qt -Total charge (C)
b. N - Number of elementary charges
c. qe – Elementary Charge = - 1.6 x 10 -19
QT  N  q
7. METHODS OF TRANSFERING CHARGE:
a. Induction - no contact between objects.
b. Contact - rubbing objects together.
8. ELECTRIC FIELD SURROUNDING:
a. positive charge - emanates from it
b. negative charge - terminates on it
c. two positive charges - field diverges
d. two negative charges - field diverges
e. one positive and one negative charge
f. between two parallel plates
g. surrounding a sphere
9. Electron Volts (eV’s)
(Elementary charges) x (volts)
W  qV
1eV  1.6 x10 19 J
9. DYNAMICS (MOVING CHARGES), CURRENTS - Current = amount of charge/time
I
q
t
I - Current, measured in amperes (A), an ampere is a coulomb/second.
q - Charge (C)
t - Time it takes for the charge to flow (sec.)
10. WORK AND POTENTIAL - To move a charge in an electric field requires work, to calculate:
V
W
q
V - Potential difference (voltage)
W - Work (J) joules
q - magnitude of the charge C
11. ELECTRON VOLT: A unit of energy (eV) which is defined as the amount of energy, or work, needed to
accelerate an electron through a potential difference of 1 volt.
1eV  1.6 x10 19 J
12. CIRCUITS AND OHM’S LAW - Ohm’s Law relates the current, voltage, and resistance in a circuit.
a. V - voltage (volts) V
b. R - resistance (ohms) 
c. I - current (amperes) A
V  IR
13. RESISTANCE OF WIRE: Depends upon 3 quantities:
a. P - A constant, which depends upon the type of material the conductor, is made. Ex: gold and silver
are good conductors; offer little resistance to the flow of electrons, p would be small.
b. L - Length of the conductor, longer length more resistance.
c. A - Area, more cross-sectional area, less resistance.
14. POWER: The rate at which energy is used in the circuit
l
R
A
V2
 I 2R
P  IV 
R
15. ELECTRIC ENERGY: Product of Power and time.
V2
t
E  Pt  IVt  I Rt 
R
2
16. SERIES CIRCUIT:
a. Current same in each element: IT=I1=I2=I3
b. Sum of the potential drops equals the total potential. (That of the battery): VT=V1+V2 +V3
c. Rt = R1 + R2 + R3 + ….. add resistors to find the total.
17. PARALLEL:
a. Voltage the same across each element: Vt = V1 = V2 = V3
b. Sum of the currents equals the total current: It = I1 + I2 + I3
c. For two resistors in parallel: 1/RT = 1/R1+1/R2+1/R3