Electrical Circuits

1
Electrical Circuits

• Section 7.3

2
SC Standards Covered

• PS 6.8 Represent an electric circuit by drawing
  a circuit diagram that includes the symbols for a
  resistor, switch, and voltage source
• PS 6.9 Compare the functioning of simple series
  and parallel circuits

3
Electrical Circuits

• Circuit closed path through which electrons can
  flow.
• Symbols to use When Drawing Circuits

AC Generator
4
Types of Circuits

• Series Circuit - current has only one path to
  travel through

5

• Parallel Circuit - contains separate branches for
  current to travel through

6
Practice Drawing Circuits

• Draw a series circuit with a battery, two light
  bulbs, and a switch
• Draw a parallel circuit with a battery, two light
  bulbs (on separate branches), a voltmeter on one
  of the branches, a switch that could turn the
  whole circuit off

7
You try

• Draw a diagram of a parallel circuit having 2
  batteries, 3 lamps, and three switches. Each lamp
  must be able to be turned off individually.

8
Comparing Series to Parallel

• Series
• Less wires
• Simpler design
• All items must work
• at the same time
• The voltage decreases as it travels through the
  circuit
• Adding more items increases the overall
  resistance of the circuit

• Parallel
• Can use one device
• on circuit at a time
• more complex and bulky design
• The voltage is the same in all parts of the
  circuit
• Adding more items decreases the resistance of the
  circuit

9
Household Circuits

• Houses are wired in parallel
• 120 V running through most lines
• What keeps the circuits from over heating?

10
Fuses and Circuit Breakers

• - Devices pull electricity from the same circuit.
  To prevent overheating, circuits are wired with
• fuse
• circuit breaker
• Fuse - contains a small piece of metal, which
  melts if the circuit heats up too muchopens
  circuit
• must be replaced

11

• Circuit breaker - piece of metal bends when it
  heats, this causes the circuit to open,
  preventing the flow of any more current
• - can usually be reset

12
Finding Resistance for a Series vs Parallel
Circuits

• Series
• Add up resistance and use that as your Rt (Total
  resistance
• Rt R1R2R3..
• Parallel
• 1/Rt 1/R1 1/R2 1/R3..