Electricity

Electricity is the flow of electrons along a given path

Protons have a (+) charge and are found in the nucleus Electric Charge Atoms are made up of charged particles Protons have a (+) charge and are found in the nucleus Electrons have a (-) charge and are free to move around the atom

Behavior of Charges Opposite charges attract Like charges repel

Conductors Electric charges are free to move from atom to atom within a material Caused by weak attraction between nucleus and electrons

Insulators Resist the flow of electrons from atom to atom within a material Caused by strong attraction between nucleus and electrons

Conducting Ability

Current Amount of charge that flows through a circuit in a given amount of time Measured in amperes (amps) (A) by an ammeter Determines the brightness of a light bulb

Current Flow in a Circuit Electrons are what are moving to cause electricity In a circuit, current flows from (+) end of battery to (-) end

Voltage (Potential Difference) Amount of electric potential energy per unit of charge Measured in Volts (V) by a voltmeter Determined by the energy source (battery)

Battery/Electrochemical Cell Converts chemical energy into electrical energy Current flows from high potential energy to low potential energy (+) end = high electrical potential (-) end = low electrical potential

Resistors Opposes the current flow in a circuit Measured in Ohms () Any device that uses energy within a circuit – a light bulb, a motor, etc.

Ohm’s Law Voltage = Current x Resistance V = I x R Voltage (V) has a direct relationship with current (I) and resistance (R) Current (I) and resistance (R) have an indirect relationship

Circuits Circuits are closed loops through which charges can travel

Circuit Symbols Wire _____ Resistor Closed switch Open switch Battery

Circuits

Types of Circuits: Series and Parallel

Series Circuits Have a SINGLE path for current to flow The current is the same in every resistor The sum of the voltage across the individual resistors is equal to the voltage of the battery. The total resistance (Req) is equal to the sum of the individual resistance values If one bulb goes out, all bulbs go out.

Applying Ohm’s Law to Series Circuits 1. Add up all resistance values to find the total resistance Req (equivalent resistance) 2. Use Req & the battery’s voltage in Ohm’s law to find the total current of the circuit. This is the same current that travels through each resistor! 3. Use the resistance & current in Ohm’s law to find the Δ V across the resistor

Use the information provided to solve for the missing variables in the circuit R1 = 17 R2 = 12 R3 = 11 ΔV = 60V Find: Req = Itot = I1 = ΔV1 = I2 = ΔV2 = I3 = ΔV3 =

Use the information provided to solve for the missing variables in the circuit R1 = 11 R2 = 7 R3 = 20 ΔV = 19V Find: Req = Itot = I1 = ΔV1 = I2 = ΔV2 = I3 = ΔV3 =

Parallel Circuits Have multiple paths (branches) for current to flow The voltage is the same across every resistor. The sum of the current in each individual branch is equal to the current outside the branches. The total resistance is found using: 1/Req = 1/R1 + 1/R2 + 1/R3 … If one bulb goes out, the rest remain lit.

Applying Ohm’s Law: Parallel Circuits 1. Add up all resistance values (1/R) to find the total resistance Req (equivalent resistance) 2. Use Req & the battery’s voltage in Ohm’s law to find the total current of the circuit. 3. Use the resistance & ΔV of each resistor in Ohm’s Law to find the current. Remember voltage is the same throughout the circuit.

Use the information provided to solve for the missing variables in the circuit. R1 = 17 R2 = 12 R3 = 11 ΔV = 60V Find: Req = Itot = I1 = ΔV1 = I2 = ΔV2 = I3 = ΔV3 =

Use the information provided to solve for the missing variables in the circuit. R1 = 11 R2 = 7 R3 = 20 ΔV = 12V Find: Req = Itot = I1 = ΔV1 = I2 = ΔV2 = I3 = ΔV3 =