Download electric forces, fields, energy, voltage, and circuits a summary guide

ELECTRIC FORCES, FIELDS, ENERGY, VOLTAGE, AND CIRCUITS - A SUMMARY GUIDE
Electric Forces and fields:
1. When charge is transferred, electrons move from one object to another.
2. If two equal-size conducting spheres are connected, conservation of charge results, which evenly divides
the charges between the two spheres.
3. In the equation for electric force (Fe = kcq1q2/r2) two positive or two negative charges multiplied by each
other yields a positive force, indicating repulsion.
4. Negatively charged objects, through induction, will cause negative charges on another conducting object
to migrate, resulting in a positive side and a negative side.
5. Electric field lines begin on positive charges and end on negative charges.
6. To find the electric field, E, on a point charge divide the F by the charge (q).
7. Like charges repel and unlike charges attract.
8. Neutral charges that have no charge, do not experience any force in E.
9. Electric fields follow the inverse square law.
Electric Potential Energy and the Electric Potential
1. The higher the potential difference between two points, the work is required to move a charge between
the two points.
2. All of the charge is on the outside of a conducting sphere, so there is no charge or electric field inside
the sphere.
3. Electric Potential (V) = KQ/R
4. To determine the electric potential at the center of a hollow metal sphere, the following needs to be
considered. Since there is no electric field inside the sphere, no additional work needs to be done after
moving the charge past the surface of the sphere. The potential from the surface of the sphere to the
center does not change, because there is no electric field to work against.
5. Unequally sized metal spheres that are connected will not hold the same amount of charge, but since
they are in contact, they will have the same electric potential.
6. Equipotential lines and electric field lines must be perpendicular to each other so that no work will be
done as a charge is moved along an equipotential line.
7. Electric field for parallel plates = V/d
8. The capacitance for parallel plates: C = oA/d and C = V/q
Electric Circuits
1. Series circuit: RTotal = R1 + R2 + R3 + …
VTotal = V1 + V2 + V3 + …
ITotal = I1 = I2 = I3 = …
2. Voltmeters placed in a circuit must be place in parallel across a resistor, light bulb, etc.
3. Ammeters placed in a circuit must be placed in series with the resistor, light bulb, etc.
4. Parallel circuit: 1/RTotal = 1/R1 + 1/R2 + 1/R3 + …
VTotal = V1 = V2 = V3 + …
ITotal = I1 + I2 + I3 + …
5. Capacitors circuits:
a. Series: 1/CTotal = 1/C1 + 1/C2 + 1/C3 + … VTotal = V1 + V2 + V3 + …
b. Parallel: CTotal = C1 + C2 + C3 + …
VTotal = V1 = V2 = V3 = …
6. An empty capacitor does not resist the flow of current, and acts like a wire.
7. A capacitor which is full of charge will not allow current to flow, and acts like a broken wire.
8. The internal resistance of a battery can be found by Ohm’s law R + RInternal = V/I
9. Resistance due to resistivity (): R = L/A