It’s shocking!

Year 10Electricity topic.

Post box activity.

• Complete the 8 questions around the room.

What is electricity?

Name three areas from where we get our electricity.

Give five uses of electricity in our homes.

Name two materials that are good conductors of electricity.

Name a material that is a good insulator of electricity.

What is the function of a fuse?

What do these symbols represent?

A

Why does a light bulb glow when you switch it on?

Two types of electricity.

1. Static2. Current

Brainpop ‘electricity’

Static electricity

• Static electricity is formed when two materials rub together and some electrons are transferred.

• The material which loses electrons becomes positive.

• The material that gains electrons becomes negative.

Wool

+ve- -Plastic -ve

Charged materials.

Attract

Repel

+ve -ve

+ve +ve

Van Der Graaf.

• Creates 2 opposing charges in the dome & wand.

Coulomb.

• The strength of a charge is measured in coulombs (C).

• It is defined as the charge transported by a steady current of one ampere in one second.

• Quick quiz.• Current electricity.• Conductor or insulator?

Current electricity

• Current electricity is the movement of electrons through a conductor.

• Electrons move from a negatively charged area to a positively charged one.

e e e e

Conductors.

• Conductors must have delocalised electrons, that is electrons which are free to move between atoms.

Conductor (metal or graphite)

Conductor or insulator?

• Test some materials and determine whether they are conductors or insulators.

• Create a table to put your results in.

Insulator Conductor

Why do some materials conduct?

• Metallic elements want to give away electrons from their outer shell, (we know this because they make positive ions).

• The electrons are not held tightly to the nucleus and are thus free to move between atoms- they conduct electricity.

• Non- metals want to take electrons (making negative ions) so they will not conduct electricity (except graphite).

Properties

ConductorsInsulators

Flex.

• Copper wires covered in plastic…why?

Circuit symbols.

• Cell Battery• Wire

Circuit symbols.

• Wire joined• Wires crossing

Circuit symbols.

• Lamp• Switch

Circuit symbols.

• Ammeter• Voltmeter

A V

Circuit symbols.

• Diode• Fuse

Circuit symbols.

• Resistor• Variable resistor (rheostat)

Memory

• Play the game of electronic memory in pairs/three’s, to help you learn the symbols.

Ratu 1st Whiringa-a-rangi

• Keywords & Mark Ex 22.01.• Components; What do they do?• Drawing circuit diagrams.

Quiz

V

12

3

4 5

67

How electrical components work?

Circuit component Function Energy

Cell/Battery Provides the electricity Electrical or chemical

Wire Carry the electricity Electricity

Lamp Provides light Elect/heat/light

Switch Controls the electricity Electricity

Ammeter Measures the current Electricity

Voltmeter Measures the voltage Electricity

Diode Controls direction Electricity

Fuse Breaks if current is too high Elect

Resistor Resist’s the flow of elect Elect/heat

Drawing circuit diagrams

• Draw circuit diagrams in pencil, using a ruler.• All wires are drawn as straight lines.• All components are drawn with a ruler or a

compass.• Ensure the cell is drawn the correct way

round.

Draw this circuit.

V

A

Draw this circuit.

Answer

AV

• Keywords 815 (8).• Mark Ex 22.01• Finish making circuit.• Drawing circuits activity & worksheet.

• Homework; Learn symbols.

Build this!

AV

Activity: worksheet.

• Walk around the lab and draw the 4 circuits that have been prepared for you.

• Now build the 4 circuits on your worksheet.

Circuit 1

A

Circuit 2

A

V

V

Circuit 3

Circuit 4

V

Circuit 5

Very bright bulb.

Circuit 6

Bright bulb 1, dimmer bulb 2.

1

2

Circuit 7

Bright bulb 1, dimmer bulb 2, dim bulb 3.

1

2

3

Circuit 8

Very bright bulbs.

Circuit 9

Very bright bulbs.

• Full keywords 115.• Mark ex 92.• Advanced making circuit.

• Homework; Ex 93

Activity: advanced circuits.

• Build the 3 advanced circuits.• REMEMBER they must be checked before you

switch them on!!

Two types of circuits.

• Series: all components in one loop.

• Parallel: 2 or more loops in the circuit.

• Mark Ex 95• Current in circuits; properties.• Voltage in circuits; properties.

Homework; Ex 96.

A

V

CURRENT (I)

• Current is a measure of the rate of flow of charge (in coulombs per second).

• The unit for current is the ampere (symbol A).• Current is measured with an ammeter, which

is connected in series with a power supply, battery, light bulb, etc.

What are the properties of current in series circuits?

• Set up a circuit with a power pack, ammeter and bulb.

• Record the reading on the ammeter and the brightness of the bulb.

• Add another bulb and ammeter in series and repeat the readings.

• Continue adding bulbs and ammeters.• What do you observe?

A1

A1

A2

A2

A1

A3

Amps in series.

• The current stay the same.• The bulbs get more dim, the more you add.• Why?• The energy gets used by each bulb as the

electrons move around the circuit, meaning the next bulb in series gets less energy and is thus more dim.

What are the properties of current in parallel circuits?

• Set up a circuit with a power pack, ammeter and bulb.

• Record the reading on the ammeter and the brightness of the bulb.

• Add another bulb and ammeter in parallel and repeat the readings.

• Continue adding bulbs and ammeters.• What do you observe?

A1

A2

A1

A2

A3

Amps in parallel.

• The current adds up.• The bulbs stay the same brightness.• Why?• The energy shared between each branch of

the circuit, so each bulb gets the same amount of energy, so have the same brightness.

CURRENT IN CIRCUITS

• In series circuits, only one path is possible around the circuit, but in parallel circuits, there is a choice of paths.

• The current is the same at all points in a series circuit.

• The current in different branches of a parallel circuit adds up to the total current entering or leaving the power supply.

1 A1 A1 A

1 A

0.5 A

0.5 A

Golden syrup racing.

• Imagine each bulb is a moat of golden syrup, it would slow you down & take up energy to each through each one.

• The more you had to wade through, the more energy you would use, but the last one you would be tired!

• Think of the electrons going through the bulb the same way.

V

VOLTAGE (V)

• Voltage is a measure of energy per charge (in joules per coulomb).

• Another name for voltage is potential difference.

• The unit for voltage is the volt (symbol V).• Voltage is measured with a voltmeter which

is connected across a power supply, battery, light bulb, etc.

What are the properties of voltage in series circuits?

• Set up a circuit with a power pack, voltmeter, ammeter and bulb.

• Record the reading on the ammeter and the brightness of the bulb.

• Add another bulb and voltmeter in series and repeat the readings.

• Continue adding bulbs and voltmeters.• What do you observe?

V V

• In a series circuit, the voltages across each component add up to the total voltage from the power source.

Voltage in series

0.4 V (used)

0.1 V (used)

1.5 V (supplied)

1.0 V (used)

What are the properties of voltage in parallel circuits?

• Set up a circuit with a power pack, voltmeter, ammeter and bulb.

• Record the reading on the ammeter and the brightness of the bulb.

• Add another bulb and voltmeter in parallel and repeat the readings.

• Continue adding bulbs and voltmeters.• What do you observe?

V V

V

Voltage in parallel

• Voltages across the branches of a parallel circuit are always the same.

1.5 V

1.5 V

1.5 V

Going for a run.

• If you have a circular track, and 10 people running, then everyone is on the same loop.

• If there are 2 choices of path; 5 people will go down path 1 and the other 5 will go down path 2.

Electrons.

• Think of the electrons as the runners; in a series circuit they only have 1 choice of path, so they all go down it.

• In parallel circuits, they spilt up and run down the different paths.

• Review current and voltage in series and parallel circuits.

• Circuits maze.• Advanced circuit making activity.

Worksheet.

• Complete the worksheet to calculate voltage and current in circuits.

• Mark Ex 96• Resistance is futile!

Homework; Ex 94.

What is resistance?

Resistance.

• Resistance makes it difficult for electrons to move through a wire.

• It’s the difference between drinking a thick shake through a thin straw and a thick straw.

• Its easier with the thick straw, because it has less resistance!

Rheostat.

• The rheostat has very thin, coiled wire, making it tough for the electrons to get through.

• As they move they give off heat energy, which why resistance reduces the voltage of a circuit.

V2 V1

Uses for resistors.

• Toaster;

Uses for resistors.

• Light bulbs;

Dimmer switch.

• http://home.howstuffworks.com/dimmer-switch1.htm

Ohms Law; Ω

• Ohms law states that resistance is equal to voltage divided by current;

• R = V ÷ I• Set up the following circuit;

A

V

Ohms Law; Ω

• Change the resistance of the rheostat, as you do record the change in voltage and current.

• What happened?

Resistance: questions.

• R = V ÷ I R(Ω) V (volts) I (amps)

0.00 0.00

1.00 0.50

2.00 1.50

3.00 6.00

2.25 4.00

12.00 5.00

15.00 7.00

Resistance: answers.

• R = V ÷ I R(Ω) V (volts) I (amps)

0.00 0.00 0.00

2.00 1.00 0.50

2.00 3.00 1.50

3.00 6.00 2.00

2.25 9.00 4.00

2.40 12.00 5.00

2.14 15.00 7.00

• Review circuit properties.• Power.

Power

• The total amount of energy gained or used per second is power.

• Power = voltage x current• P = V x I• Power is measured in watts.• Complete the table using the formula.

P = V x IVoltage Current Power

0.0 0

1.0 0.5

2.0 2.0

3.0 4.2

1.6 6.4

1.8 9.0

6.0 12.0

P = V x IVoltage Current Power

0.0 0

1.0 0.5

2.0 2.0

3.0 4.2

1.6 6.4

1.8 9.0

6.0 12.0

• Conserving energy and reducing your power bill, to save you money.

Conserving electricity

• Why should we conserve electricity?• Can you think of some ways to save power,

and money?

Small steps.• Fix leaking taps• A leaky tap that drips every second can waste 10,000 litres of water a year.

This can usually be easily fixed by changing a washer and for hot water, can save $20 - $30 per year on your power bill.

• Turn appliances off at the wall • Switch off lights when you leave the room. Turn appliances off at the wall

– even when on standby, appliances use a surprising amount of electricity. This includes unplugging phone chargers, which continue to use energy even when not plugged into phones.

• Turn off your heated towel rail when the towels have dried• Turning off the towel rail after four hours, rather than leaving it on all the

time can save you up to $100 on your power bill per year. • Try to use cold washes to wash your clothes rather than hot• A warm wash uses as much energy as a drier cycle. • Try to use your clothesline more often instead of your dryer• Hanging out the washing saves money and reduces the amount of

moisture in your home, and the suns rays will kill harmful bacteria and germs.

• Keep the heat in your home — close windows and curtains at night

• This makes the most of the heat stored in your house during the day.

• Turn off your beer fridge• Beer fridges are often old, inefficient and often half full.

Turning off your beer fridge could save you $100 per year. • Consider taking a shower instead of a bath• Short showers use less energy and water than baths. You can

save even more by fitting a low flow shower head. • Reduce your power use and try to use your microwave more• Microwaves use less energy than stoves or ovens. If possible,

switch the microwave off at the wall after use – over time the clock on a microwave can use more energy than cooking the food!

• Turn your computer monitor off — it uses less power than standby

• Instead of using a screensaver which actually consumes energy, turn your computer monitor off when you aren't using it. Your monitor uses more energy than your hard drive!

• Draught-proof your home to make it easier to heat• Use draught stoppers behind your doors, and seal cracks

around windows, especially in the colder months. Draught stoppers can be brought from any hardware store - or you can make your own.

• If you're building, get advice on home energy efficiency• Talk to an Eco Design Advisor about what you can do to make

your home healthier and more energy efficient. Check out the Eco Design Advisor website for more information.

Medium steps• Replace your regular light bulbs with eco-bulbs• Replacing your highest-use lights with CFLs can save

on your power bill. They use 20% of the energy of other bulbs and produce the same amount of light. Put them in the five most-used areas of your home.

• Keep the heat in your home and consider installing thermal curtains with good quality lining

• Thermal curtains are specially designed to increase the insulation around your windows and retain more heat within your home.

• Reduce your power use — install a timer on your heater

• A timer will ensure you heat your house only when you are home.

• Consider the size of the room when choosing a heating system

• More guidance on finding the proper sized heater for your room can be found on the Consumer Institute website.

• Find out how much power you are using — get an energy audit done on your home

• An energy audit will allow you to identify cost savings that may be able to be made from reducing energy use in your home.

Big steps

• Insulate your home• Insulation makes your house easier and cheaper to

heat. Insulation can be found at most hardware stores, or search for it in the Yellow Pages under ‘Insulation Thermal’.

• Choose energy efficient appliances — look for the Energy Star label or star rating

• Use the Energy Star website to choose products which use less energy.

• Wrap your hot water cylinder and pipes to stop heat escaping

• If your water pipes are hot to touch, valuable heat is escaping which is costing you money. Hot water cylinder wraps can be brought at most hardware stores and will reduce the amount of heat lost from the water in the cylinder.

• Find out where you are using power — invest in a power monitor

• Power meters test how much electricity your appliance uses when running and when in standby mode.

• Install a solar hot water heating system• Hot water heating makes up about 30% of average household

energy use. A solar hot water heating system provides plenty of hot water and saves up to 75% off your hot water bill see the Solar Smart website for details on solar water heating.

• Complete the 2 study sheets for the electricity test on FRIDAY.

• REVISE at home tonight.