Circuits

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

Types of CircuitsTypes of Circuits

Series and Parallel

What is a circuit?

• Electric Circuit – path that an electric current follows.–Open Circuit – break in path.

Electricity can NOT flow through.

–Closed Circuit – No breaks. Electricity can flow through.

Circuit Diagrams

Series CircuitsIn a series circuit, the current has only one

pathway to travel.

e-

e-

e-

Series Circuit

If one bulb goes out, they all go out

• Creates an open circuit

Series Circuits• Current is same throughout circuit

(through each resistor).

• Current in entire circuit decreases with increased resistance (cumulative: add resistance to get total resistance).

Checkpoint• Series Circuit

1. What is total resistance?

2. What is the current?

3. What happens when one resistor (light bulb) burns out?

Parallel CircuitIn a parallel circuit, the current has multiple

pathways to follow.

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e-e- e-

Parallel Circuit• Individual path for

each item connected

• If one item goes out the others stay on

•Still a closed circuit

• Voltage in each path is same

• Total current in circuit increases if another path is added, the total resistance is reduced

Using Chemical Cells (Batteries)

Series

• Makes “Battery”

• Increases Total Voltage

Parallel

• Makes “Battery”

• Total voltage does not change

•Makes batteries last longer

Complex Circuits• Combination of series and

parallel circuits

–In your house

If we try to send too much current (too many electrons, too fast) through a circuit, the circuit

will get hot and may cause a fire !

A FUSE has a metal strip that will melt if it gets too hot. This prevents the circuit from melting in another spot.

Now you must replace the fuse.

A CIRCUIT BREAKER has a metal strip that bends as it is heated. When it bends too much, it activates a switch that breaks the circuit.

Once reset, the circuit breaker can be used again.

Lab

1. Series Circuit with 3 light bulbs

2. Parallel circuit with 3 light bulbs

3. Complex circuit with 2 bulbs in series and the 3rd in parallel to the other 2.