Electricity Unit Overview Wednesday, April 1, 2015

Unit 9: Electricity Wednesday, 4/1 Take out your notes and retrieve a calculator for you open note quiz. Upcoming dates: Monday, 3/30 – Wednesday, 4/1 –arena scheduling window Monday, 3/30 – delayed start; 1 st and 3 rd periods only Monday, 3/30 – Wednesday, 4/1 –arena scheduling window Wednesday, 4/1 – delayed start; 2 nd and 4 th periods only Thursday, 4/2 – 5SW extra credit due by 4:30 Tuesday, 4/7 – open note quiz (DATE CHANGE) Tuesday, 4/7 – last day to turn in missing electricity assignments Thursday, 4/9 – Electricity test (grade will go on the 6SW) Friday, 4/10 – End of 5SW

Quiz

Types of Electricity Dynamic Static Direct Current (DC) Alternating Current (AC) Series ComplexParallel Unit Overview Motion of free charges No motion of free charges

Electric Current The continuous flow of electrons through a conducting metal.

Alternating Current Flow of current that periodically changes direction Produced in power plants Current from a wall outlet changes direction 120 times per second

Direct Current The flow of current in one consistent direction Examples Batteries Solar cells Current from a battery travels from the positive terminal to the negative terminal.

Common Language

Note Taking Guide QuantitySymbolDefinitionUnitMeasuring Device voltage current resistance

Voltage Voltage (V) (also know as Potential Difference) can be thought of as the force pushing electric charges along a conductor. Voltage between two points creates an electric field. Measured in Volts (V)

Voltmeter a device that measures electric potential difference, must be connected in parallel

Current Electric current (I) is the movement of electric charge in a conductor. Measured in Amps (A)

Ammeter a device that measures current attached in series

Resistance Resistance (R) is a measure of how difficult it is to push the charges along. The energy is transformed at the resistor (potential energy is converted). Examples: light bulb, charging your phone, making coffee, etc. Measured in Ohms ( 

Note Taking Guide QuantitySymbolDefinitionUnitMeasuring Device voltageVEnergy in the circuitVoltsVoltmeter currentIRate of flowAmpsAmmeter resistanceROpposes currentOhmsΩOhmmeter

Measuring voltage and Resistance On the back table there are circuit boards and multi- meters (you can use as a voltmeter and an ohmmeter.

Directions Part 1 Measure the voltage of the battery Turn the dial to 20 on the multi-meter (top left) Place one probe on the positive (+) end and one probe on the negative (-) end. Record the voltage Part 2 Measure the resistance of the resistors Turn the dial to 200 (bottom left) Place a probe on each side of the resistor Record the resistance for each resistor (green, blue, and red) Part 3 Using the items in your box create a circuit that will illuminate a bulb.

Ohm ’ s Law Ohm's Law deals with the relationship between voltage and current in an ideal conductor. Ohm's Law is given by: V = I * R

Example A flashlight that is powered by 3 volts and uses a bulb with a resistance of 60 ohms. What is the current flowing through the circuit?

Electrical Circuit Terminology Circuit – a path that allows electricity to flow Circuit diagram – a simplified representation of an electrical circuit that shows only the electrical connections of elements in a circuit. Complete circuit – a circuit with an unbroken path that allows electrons to flow. We will study two types of circuits: Series circuit Parallel circuit

Practice

Types of Electricity Dynamic Static Direct Current (DC) Alternating Current (AC) Series ComplexParallel Unit Overview

Resistors can be connected in series; that is, the current flows through them one after another. Series Circuits

Kirchhoff’s Rules Loop Rule: The sum of the potential differences (voltage) around any closed circuit loop is zero.

Resistor Circuits Series 1. total resistance is the sum of the separate resistors separate resistors R T = R 1 + R 2 + R current is the same through each resistor I T = I 1 = I 2 = I 3 = total potential difference is the sum of each V T = V 1 + V 2 + V In other words, in a series circuit, resistance and voltage add, but current stays the same.

Series Circuit Example