Circuits are designed to control the transfer of Electrical Energy Chapter 9: Circuits are designed to control the transfer of Electrical Energy

Page Types of Circuits Series Parallel

SERIES vs PARALLEL 1 path several paths Use the analogy of the waterslide, if climb 12 steps then you must fall 12 steps to start at the beginning again. If anyone is the single file line stops then all stop

SERIES PARALLEL One bulb goes out they ALL go out! One bulb goes out the others do NOT!

VOLTAGE Vsource = Vloads total SERIES PARALLEL The sum of the Voltages lost on the loads equals the Total voltage supplied by the source Vsource = Vloads total The sum of the Voltages lost on the loads of a single path equals the total voltage supplied by the source Single slide waterway versus multiple choices at the top.

V CELL EFFECTS Same V SERIES PARALLEL Cells in series increase voltage but battery life is shortened Cells in parallel keep same voltage as single cell but battery life is lengthened Single slide waterway versus multiple choices at the top. V Same V

CURRENT SERIES PARALLEL Same throughout Pathways differ Current entering a junction point = current leaving Highest current on paths with less resistance

RESISTANCE SERIES PARALLEL Resistors in series increase total resistance (therefore current I decreases – slows down flow) Resistors in parallel will decrease the total resistance of the circuit (therefore current increases-faster flow) Waterslide analogy with the water stopping offering more resistance and you would slow down, all other electrons would slow down as well due to the action-at-a-distance forces, yet another dry spot would slow you down even more! For a complete summary see page 294 in text. Questions page 290 1-5, and 293 1-5

Protecting Household Circuits page 296 Circuit Breakers Fuse Grounding Terminals

CIRCUIT BREAKERS Bimetallic strip heats up and bends to prevent excessive current from entering the home

FUSE Contains a metal conductor which melts when excessive current runs through it and thus breaks the circuit. It needs to be replaced to restart the circuit.

GROUNDING TERMINALS The round prong on an electrical plug, prevents shock by allowing excess current to flow to the ground Reading Check questions page 297 #1-6 Check your understanding page 303 #1-10 especially questions 7-10.

Resistors in series and parallel Core Lab Resistors in series and parallel Lab 9-1F page 300

Section 9-2 page 304 The Power of Electricity Electrical Energy -the ability of moving electrons to do work - measured in Joules (J) Video clips

ELECTRICAL POWER POWER How fast Energy changes from one form to another heat E electrical E light E sound E Measured in watts (W) 1W = 1J/1s Use the analogy of cars racing up a hill, both have the same distance to travel and have the same mass however the newer one is more powerful and will get their faster.

Electrical Energy Costs Depends upon 3 factors Voltage Drop Electrical Current Time

POWER RATING A measurement of how much electrical energy an electrical device consumes per second of use On devices such as a hairdryer, a 1500 W hairdryer will use 1500 J of energy for each second it is on!

E P t E = P ∙ t Calculating Energy Consumption E = energy (J) P = power (W) t = time (s)

Example: How much electrical Energy is consumed by a 60W light bulb if it is left on for 25 min? P = 60 W t = 25 min E = Pt Convert time to seconds: t = 25 min x 60 sec = 1500 sec 1 min E = (60 W)(1500 sec) = 90,000 J or 9 x 104 J Also include conversions to kWh where 1 kW = 1000 W. 60 W x 1 kW/1000W = 0.060 kW. Use some electricity bills to help illustrate why kWh are used. Also discuss some careers in electricity such as electrician and photocopier technician especially increased numbers for females in the trade related careers. Get the guidance counsellor in to discuss options. Practice problems on page 308 # 2 and 3

A LARGER Unit for Energy Recall: 1 Joule = 1 Watt × 1 second For home usage increase W to kW and sec to hr New larger units: kW∙h kilowatt-hour Energy labels on appliances are in kW∙h

To calculate the cost of electrical usage in the home: COST OF ELECTRICITY To calculate the cost of electrical usage in the home: Multiply the kW∙h used by the rate charged by the electrical company per kW∙h. Current rate = $0.10/kW∙h

Example: Which will save you more money on your yearly electrical bill, stove A which has an energy rating of 504 kW∙h or stove B with a rating of 735 kW∙h per year of average use? Cost = (energy rating)(rate per kW∙h) Stove A=(504 kW∙h)($0.10/ kW∙h) =$50.4 a year Stove B=(735 kW∙h)($0.10/ kW∙h) =$73.5 a year Stove A is more energy efficient! Provide examples of careers in electricity such as an electrician and photocopier technician Other example, average Newfoundland power consumption is approximately 1288 kW∙h per month. Calculate average monthly and yearly bills of Newfoundlanders Complete activity 9-2B in the text on calculating the cost of elec

Section 9.3 page 314 Electrical Energy in the Home Efficiency is the % of energy that is converted to a useful form. Efficiency = useful energy output × 100% total energy input Read the did you know on page 314. Discuss heating a lunch in the oven versus microwave versus on top of a light.

Efficiency = E output x 100% E input Example: How efficient is a bulb that uses 7000 J to produce 4500J of light? Efficiency = E output x 100% E input = 4500J x 100% 7000J =64.3% The bulb has an efficiency of 64.3 % Complete the practice problems on page 318.

EnerGuide Labels Details how much energy an appliance uses in a year in kW∙h and compares to other appliances

Electricity and the Environment Section 9.4 Page 324 MECHANICAL ENERGY is energy of motion, it requires moving parts A GENERATOR converts Mechanical Energy into Electrical Energy Examples include: Windmills, Hydroelectricity, Geothermal power, Nuclear power

A GENERATOR consists of a coil of wire and a magnet - one moves in relation to the other to generate electricity

3 Types of Generators: 1. Hydroelectric –uses falling WATER to turn a turbine 2. Thermal Energy – uses heat from BURNING FOSSIL FUELS to boil water and the resulting steam turns a turbine 3. Nuclear Energy – uses heat from a NUCLEAR REACTION to boil water and the steam turns a turbine

How does Electricity get to our homes? The electrical energy generated is transmitted over LARGE distances using HIGH voltage and low current.

Transformers Electrical device that changes voltage Step UP increase voltage for transmission and Step down decrease voltage for use in our homes where it is provided as 120V and 240V service.

Degree of environmental damage When Deciding what Energy source are appropriate for an area, several factors need to be considered: Safety Cost of production Degree of environmental damage

Alternate Energy Sources include: Wind Energy Solar Energy Fuel Energy

New Energy Development is Limited by such factors as: Cost Availability of Materials Property of Materials