1. Topic 3 Continued: Resistors
Resistors are used to control the current or voltage in order to protect other loads in the circuit. They are usually made from a ceramic core that is coated with a metal, a metal oxide, a metal film or wire.

2. Variable Resistor
These resistors have the ability to change their resistance when exposed to temperature, light, voltages etc. These are used in many electronic devices like dimmer switches, fridges, volume controls etc.

3. Two Types of Circuits
1. Series: They have only one path for all the current to travel down. If there is a break in the circuit there is no where else for the electrons to go so the flow will stop.

4. 2. Parallel: They have multiple paths, (at least two), for all the current to travel down. If there is a break in the circuit the electrons will continue to flow through the other paths.

5. Wiring
Most residential and commerical circuits are parallel.
The voltage across all loads in parallel circuits is the same. If you use an appliance it will not use up voltage for a different appliance
Current increases as each path becomes closed. The current in the appliance closest to the source will increase as more appliances are turned on.
More current means temperature increases. If the temperature rises too high, (too many things are plugged in/turned on), a fire will start or a fuse will blow, (breaking the circuit).

6. Know Chart below (page 291)
Factor
Effect
Length
Resistance Increases as length increases.
Cross Sectional Area
Resistance decreases as area increases.
Temperature
Resistance Increases as temperature Increases.
Material
Some metals allow flow more easily than others
Read Pages 283 – 291
Complete Designing Circuits Worksheet