1. Circuits and Wiring Lesson 10

2. Important Electrical Concepts  Voltage, Current and Resistance Voltage (V)- measured in volts Voltage (V)- measured in volts Difference in electrical potential is used to drive electrons around circuitsDifference in electrical potential is used to drive electrons around circuits Current (i)- measured in Amps Current (i)- measured in Amps The measure of electron flow around a circuitThe measure of electron flow around a circuit Resistance (R)- measured in Ohms Resistance (R)- measured in Ohms How difficult it is for an electron to flow though a material.How difficult it is for an electron to flow though a material.

3. How are the three concepts related? Ohm’s Law V= i x R  Voltage is equal to the current times the resistance.  If any two quantities are known you can solve for the missing quantity.

4. Current Flowing Through Circuits  Current only flows if it has a path towards lower voltage  Closed Circuit: when a path exists  Open Circuit: when a path does not exist Open CircuitClosed Circuit

5. Using Open and Closed Circuits  Buttons and switches Used to open and close a circuit Used to open and close a circuit  If a circuit involves a motor a button can be used to stop the motor from spinning.

6. Batteries  Supply a portable power source or voltage  How do batteries work? Batteries are filled with chemicals that produce electrons Batteries are filled with chemicals that produce electrons The electrons are drawn to an electrode inside The electrons are drawn to an electrode inside You can connect a circuit to the plus (+) and minus (-) ends You can connect a circuit to the plus (+) and minus (-) ends Electrons will flow from – to + Electrons will flow from – to +

7. Circuit Diagrams: The Symbols  Many different symbols are used:

8. Circuit Diagrams: The Symbols

9. Circuit Diagrams  Importance Visualize circuit without actually constructing Visualize circuit without actually constructing Record circuits that have been designed Record circuits that have been designed Tool for analyzing the circuit Tool for analyzing the circuit  Remember! A circuit is a path for electrons A circuit is a path for electrons

10. Can you identify the elements in the circuit?

11. Motor Circuits  Switching direction of motor Depends on current direction Depends on current direction Easily changed by swapping battery terminals connected to motor Easily changed by swapping battery terminals connected to motor It is easy to create a circuit that switches the direction of the motor It is easy to create a circuit that switches the direction of the motor

12. Motor Circuits  Motor Speed Related to current applied to the motor Related to current applied to the motor More Current = More Force = Faster Speed More Current = More Force = Faster Speed How do you vary the current How do you vary the current Remember: Ohm’s law relationship between voltage, current and resistanceRemember: Ohm’s law relationship between voltage, current and resistance Use variable voltage sourceUse variable voltage source Change resistance of motorChange resistance of motor