1. Current- the movement of charge. Symbol is I, unit is the Ampere (A) I = q/t 1 A = 1 C/s Conventional current- from the positive terminal to the negative terminal. Drift velocity- the speed in which individual electrons move within the conductor, opposite the electric field. The drift velocity is relatively small.

2. Resistance- the opposition to the flow of charge by a material or device. Symbol is R, unit is ohms (  ). Ohms law R = V/ I or V = IR Resistance depends on the following factors: Length – short wires have less resistance Area- thick wires have less resistance Material- different materials have different conductivity of charge Temperature- heat slows the flow of charge.

3. Power Power is energy used per time. The unit of power is a Watt = Joule/sec P= PE/t, or P=IV You can use Ohm’s Law to substitute in the equation, creating two other equations, P=I 2 R, or P=V 2 /R.

4. Series Circuits In a series circuit, there is only one pathway for current, so the current is the same everywhere. Resistors add up in series. R+R+R=R total Kirchhoff’s rule- Voltage drops must equal the starting voltage, or V-IR-IR=0. Ohm’s Law holds for all parts of the circuit.

5. Advantages/Disadvantages Advantages of a Series Circuit- easy to hook up, needs fewer wires, the current is the same everywhere. Disadvantages- uses more current, if one device goes out, or a wire comes loose, the whole circuit stops working.

6. Parallel Circuits In a parallel circuit, there are multiple pathways for current. Resistance in parallel is less than the smallest parallel branch. 1/R + 1/R = 1/R total Voltage is the same across both branches. Current divides up in parallel, path of least resistance gets more current. V/R=I

7. Advantages/Disadvantages Advantages of Parallel- the resistance is lower, more current can be used effectively, more devices can be hooked into the same voltage source. If one device goes out, the others continue working. Disadvantages of Parallel- more difficult to connect, uses more wires.