Current- the movement of charge.

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 (W).
• 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 PIV
• You can use Ohms Law to substitute in the
  equation, creating two other equations, PI2R, or
  PV2/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. RRRRtotal
• Kirchhoffs rule- Voltage drops must equal the
  starting voltage, or V-IR-IR0.
• Ohms Law holds for all parts of the circuit.

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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/Rtotal
• Voltage is the same across both branches.
• Current divides up in parallel, path of least
  resistance gets more current. V/RI

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.