Circuits and WiringCircuits and WiringLesson 10Lesson 10

Important Electrical ConceptsImportant Electrical Concepts Voltage, Current and ResistanceVoltage, Current and Resistance

Voltage (V)- measured in voltsVoltage (V)- measured in volts• Difference in electrical potential is used to drive Difference in electrical potential is used to drive

electrons around circuitselectrons around circuits Current (i)- measured in AmpsCurrent (i)- measured in Amps

• The measure of electron flow around a circuitThe measure of electron flow around a circuit Resistance (R)- measured in OhmsResistance (R)- measured in Ohms

• How difficult it is for an electron to flow though a How difficult it is for an electron to flow though a material. material.

How are the three concepts How are the three concepts related?related?

Ohm’s LawOhm’s Law

V= i x RV= i x R Voltage is equal to the current times the Voltage is equal to the current times the

resistance.resistance. If any two quantities are known you can solve If any two quantities are known you can solve

for the missing quantity.for the missing quantity.

Current Flowing Through CircuitsCurrent Flowing Through Circuits Current only flows if it has a path towards Current only flows if it has a path towards

lower voltagelower voltage Closed Circuit: when a path existsClosed Circuit: when a path exists Open Circuit: when a path does not existOpen Circuit: when a path does not exist

Open Circuit Closed Circuit

Using Open and Closed CircuitsUsing Open and Closed Circuits

Buttons and switches Buttons and switches Used to open and close a circuitUsed to open and close a circuit

If a circuit involves a motor a button can be If a circuit involves a motor a button can be used to stop the motor from spinning.used to stop the motor from spinning.

BatteriesBatteries

Supply a portable power source or voltageSupply a portable power source or voltage

How do batteries work?How do batteries work? Batteries are filled with chemicals that produce electronsBatteries are filled with chemicals that produce electrons The electrons are drawn to an electrode insideThe electrons are drawn to an electrode inside You can connect a circuit to the plus (+) and minus (-) endsYou can connect a circuit to the plus (+) and minus (-) ends Electrons will flow from – to +Electrons will flow from – to +

Circuit Diagrams: The Circuit Diagrams: The SymbolsSymbols

Many different symbols are used:Many different symbols are used:

Circuit Diagrams: The Circuit Diagrams: The SymbolsSymbols

Circuit DiagramsCircuit Diagrams

ImportanceImportance Visualize circuit without actually constructingVisualize circuit without actually constructing Record circuits that have been designedRecord circuits that have been designed Tool for analyzing the circuitTool for analyzing the circuit

Remember!Remember! A circuit is a path for electronsA circuit is a path for electrons

Can you identify the elements in Can you identify the elements in the circuit?the circuit?

Motor CircuitsMotor Circuits

Switching direction of motorSwitching direction of motor Depends on current directionDepends on current direction Easily changed by swapping battery terminals Easily changed by swapping battery terminals

connected to motorconnected to motor It is easy to create a circuit that switches the It is easy to create a circuit that switches the

direction of the motordirection of the motor

Motor CircuitsMotor Circuits Motor SpeedMotor Speed

Related to current applied to the motorRelated to current applied to the motor

More Current = More Force = Faster SpeedMore Current = More Force = Faster Speed

How do you vary the currentHow do you vary the current• Remember: Ohm’s law relationship between voltage, Remember: Ohm’s law relationship between voltage,

current and resistancecurrent and resistance

• Use variable voltage sourceUse variable voltage source

• Change resistance of motor Change resistance of motor