Equipment 5.4 is covered earlier on in the spec in some detail. This lesson combines 5.4 and 5.5. This lesson also recaps unit 1 and calculating kilowatt hours. It adds in appliance efficiency. Reiterate the usefulness of this equation (it crops up a lot) link to maths as it is how they calculate a percentage in Maths. Calculators A r

Recall: Calculations! Charge = Current x Time Energy = Potential difference x charge Potential Difference = current x resistance What are charge, current and time measured in and what are the symbols? Calculate the charge flowing in 50s when the current is 5A Calculate the energy transferred when the charge is 30C and the potential difference is 4V Calculate the energy transferred in 60 s when a current of 0.5A passes through a 12Ω resistor Students covered these cacluations in the last unit The last question requires the combination of calculations 1) Coulombs (Q) Amps (A) Seconds (t) 2) 50 x 5 = 250C 3) 30 x 4 = 120J 4) V= I x R 0.5 x 12 = 6v Q = I x t 0.5 x 60 = 30C E = V x Q 6V x 30C = 180J

4 6 8 Lesson intentions: Date and title: 25 April, 2019 S t e p s t o S u c c e s s Learning outcomes: 4 6 12 8 Key words:

4 6 8 Lesson intentions: Date and title: Appliances and efficiency How much does it cost to watch Netflix for an hour? Date and title: Appliances and efficiency 25 April, 2019 S t e p s t o S u c c e s s Learning outcomes: Describe the factors that affect the cost of using various electrical devices. Calculate the power rating of a device from the energy transferred and the time of operation Compare a range of electrical devices in terms of efficiency using calculations to support any conclusions. 4 6 12 8 Key words: Power, kWh, Efficiency, Waste, Useful

Bigger picture Topic Fuses and Circuit breakers ACDC Plugs Electrical Power Topic Electricity in the home Energy Transfer Appliances and efficiency

Energy and Power E= P x t Power (W) = Current (A) x Voltage (V) Energy (J) = Power (W) x Time (s) E= P x t Power (W) = Current (A) x Voltage (V) P= I x V Reminder of the two power equations. The first has been rearranged as the energy is the subject in this lesson.. You can work through the energy equation as it makes sense…. How much energy iis used by something… the amound of power multiplied by the time it is on. Give an example.. If you were being paid £10 an hour and you worked for 10 hours hwo much would you be paid etc, A 3000W heater is used for 18000 seconds.. How much energy does it use?

Energy (J)= Power (W) x Time (s) A 3000W heater is used for 18000 seconds.. How much energy does it use? Energy (J)= Power (W) x Time (s) Energy = 3000 x 18000 Energy = 54,000,000 J Can we simplify? Have a student run through the working. Highlight the alternative unit and why it is that Highligh that it is just a different unit for energy When you have the answer question them about bills.. Do we want to have people looking at huge numbers on bills? Why not? Ask them what we could do instead and highlight the unit kWh for higher ability you can ask why aren't we working in kJ or similar (because we have gone into a non-metric progression using 60 instead of 10s, 100s and 1000s) Power (kW) x Time (h) 3 x 5 15 kWh

Kilowatt Hours! Energy companies use units of electrical energy called kilowatt-hours (kWh) or simply units. 1 unit (kWh) = 3,600,000 j! Units used = power x time (kWh) (kW) (h) The cost per unit depends on the company, in the UK between 10-15p. Remind them of this Talk about the equation for this and why it is useful to know (link to energy bills and costs)

Ai) 5 x 3000 = 15000 J Aii) 100 x (24 x 60 x 60) = 8,640,000 J Bi) (3x1000) x (5x6) x 6 3000 x 30 x 6 = 540,000 J Bii) 1000 x (30x60) = 1,800,000 J Show all workings

You leave a 3kW heater on in your room You leave a 3kW heater on in your room. You put it on at 8am and leave it on until 4pm. How many units (kWh) of electricity are used? Units of electricity = kW x h 3 x 8 = 24 kWh = 24 Units A 2500 W Oven is used for 30 minutes. How many units (kWh) of electricity are used? (2500/1000) x 0.5) 2.5 x 0.5 = 1.25 kWh = 1.25 Units

Efficiency = OUTPUT power (W) input power (W) (x100) to get a percentage! Walk through the equation noting that efficiency can be given as a decimal or multiplied by 100 to get a percentage Recap that they have covered this equation before an that it comes up lots throughout the different disciplines! Highlight that it can be rearranged but percentage efficiency MUST either convert into a decimal first or divide by 100 afterwards

Highlight they will need to rearrange the equation to work this out Highlight they will need to rearrange the equation to work this out.. You may want to go through the rearrangement on the board depending on level of class. Ai 80W Aii 5W b) A halogen bulb puts out 25W of light (100 x 0.25) An LED puts puts out 1.8W (2 x 0.9) Therfore 25/1.8 = 13.9 rounded to 14 bulbs would be required to produce the same LIGHT.

In no more than 2 sentences summarise the key points from this lesson