Electricity Unit OverviewThursday, April 2, 2015

Unit 9: Electricity Thursday, 4/2

Pick up handout from the Physics bin

On the diagram write what you think the difference between the two types of electricity are.

Upcoming dates: Thursday, 4/2 – 5SW extra credit due by 4:30 Tuesday, 4/7 – last day to turn in missing electricity assignments Wednesday, 4/8 – open note quiz (DATE CHANGE) Friday, 4/10 – Electricity test (grade will go on the 6SW) Friday, 4/10 – End of 5SW

Types of Electricity

Dynamic Static

Direct Current (DC)

Alternating Current (AC)

Series ComplexParallel

Unit OverviewMotion of free charge

s

No motion of free charge

s

Electric CurrentThe continuous flow of electrons through a

conducting metal.

Alternating CurrentFlow of current that periodically changes

directionProduced in power plants

Current from a wall outlet changes direction 120 times per second

Direct CurrentThe flow of current in one consistent direction

ExamplesBatteriesSolar cells

Current from a battery travels from the positive terminal to the negative terminal.

Common Language

Note Taking GuideQuantity Symbol Definition Unit Measuring

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)

VoltmeterVoltmetera device that measures

electric potential difference, must be connected in parallel

CurrentElectric current (I) is the movement of

electric charge in a conductor.Measured in Amps (A)

AmmeterAmmetera device that measures current

attached in series

ResistanceResistance (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 GuideQuantity Symbol Definition Unit Measuring

Device

voltage V Energy in the circuit

Volts Voltmeter

current I Rate of flow Amps Ammeter

resistance R Opposes current OhmsΩ Ohmmeter

Measuring voltage and Resistance

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

DirectionsPart 1

Measure the voltage of the batteryTurn 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 2Measure the resistance of the resistors

Turn the dial to 200 (bottom left)Place a probe on each side of the resistorRecord the resistance for each resistor (green, blue, and red)

Part 3Using the items in your box create a circuit that will

illuminate a bulb.

Ohm’s LawOhm's Law deals with the relationship between

voltage and current in an ideal conductor.

Ohm's Law is given by:

V = I * R

ExampleA 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 circuitParallel 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

KirchhoffKirchhoff’’s Ruless Rules

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

Resistor CircuitsResistor CircuitsSeries

1. 1. total resistancetotal resistance is the sum of the is the sum of the separate resistorsseparate resistors

RRTT = R = R11 + R + R22 + R + R33 + ... + ...

2. 2. currentcurrent is the same through each resistor is the same through each resistor

IITT = I = I11 = I = I22 = I = I33 = ... = ...

3. 3. total potential differencetotal potential difference is the sum of each is the sum of each

VVTT = V = V11 + V + V22 + V + V33 + ... + ...

In other words, in a series circuit,In other words, in a series circuit,resistance and voltage add,resistance and voltage add,but current stays the same.but current stays the same.

Series Circuit Example