Electric Circuits Goals: electricity, voltage, current, resistance, ohm’s law, Kirchoff’s laws, power and energy

Electricity Electricity – flow of electrons or……… the flow of electric charge One of the six forms of energy: cause a change or do work W = F x d Nm J W = F x d Nm J Circuit – pathway for electrons parts include: wire, battery (source), loads, resistors and a switch that………. parts include: wire, battery (source), loads, resistors and a switch that………. Opens and Closes the circuit

Current and Voltage Current – the movement of electric charge Symbol “I” Measured in amps, flashlight is about 1/2 amp Measured with an ammeter Voltage – electrical potential or potential difference that causes the flow of charge Energy supplied by moving charge Symbol “V” measured in volts Measured with a voltmeter each cell = 1.5 v Batteries are cells connected in series

Resistance and Ohm’s Law Resistance – the opposition to flow Varies with each load: blow drier vs bulb Symbol R or “Ω” measured in ohms Resistors control flow in circuits Fixed or Variable (potentiometers) Measured with a ohmmeter Ohm’s Law relates voltage, current and resistance V = I R V = I R

Series Circuits Series – all loads are on one pathway One load can open the circuit Current remains the same on each load Total Resistance is the sum total of each resistor or load There is a voltage drop across each load Total Voltage at the source is the sum of all voltage drops Kirchoff’s voltage law Problems – add Rs to get total, use total V and total R to calculate each voltage drop

Parallel Circuits Parallel circuits have an alternate pathway for electrons Branch Circuit Current entering a branch must exit Kirchoff’s current law Voltage stays the same across each branch advantage of its use household circuits each branch can be opened independently since each branch has the same voltage, the current can be calculated independently by knowing the resistance and resistances totaled since each branch has the same voltage, the current can be calculated independently by knowing the resistance and resistances totaled Short Circuit

Electrical Power and Energy Power – the rate at which work is done or energy converted to another form P = w/t fd/t joules/sec watts P = w/t fd/t joules/sec watts P = I V amp volts joules/sec kW Electric Energy – how long energy is converted EE = P t kWh Cost = kWh x cents/kWh Direct Current – energy flows in one direction produced in batteries Alternating Current – current flows forth and back in conductor 60 times every second 60Hz Adapters Transformers step up and step down voltage

Joke………… When is Electricity important to us? AnswerAlways What is so funny about that? Nothing but……………. I can’t even laugh without electricity