1. Power 3.1h power as energy transferred per unit time: E=Pt 3.1i The power transferred using: power = voltage × current (P=VI) power = current2 ×resistance P = I 2R

2. 1.Match up the electrical quantities, with their abbreviations and units. 2.How many volts in 1kV? 3.How many grammes in 0.6kg IVE PampereΩ EnergyOhmsVoltage voltsresistancewatts joulePowercurrent

3. Energy and Power The power rating of an appliance is given on the back of the appliance. Power rating is the rate at which an appliance transfers energy. It is measured in joules per second, called watts. One watt is one joule per second (1W= 1J/s) P = E/t where P is Power in watts (W) E is energy in joules (J) T is time in seconds (s)

4. Example A portable fan transfers 1800 joules of energy in 60 seconds. What is its power rating? P=E/t = 1800J/60s = 30W

5. 1.What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds? 2. A fridge uses 540,000J of electrical energy in 1 hour. What is its power rating? 3.A modem uses 10,000J of energy in 30 minutes. What is its power rating?

6. Power can also be calculated using the voltage and current. Power = Current x Voltage P=VI

7. Example 2.If you have a filament bulb and it has a potential difference of 200V across it and a current of 0.2A running through it. At what power is the bulb operating at?  P = IV  P= 0.2A x 200 V  P= 40W

8. Electric Circus – group size 4 1.Calculate the power of the following appliances. 2.Which appliance will transfer the most energy? 3.Calculate the energy transferred by the energy saving lightbulb if on for 1.5 hours every day for 1 week? 4.Calculate the energy transferred by the electric car in kW. AppliancePower kettle hairdryer Printer hob TV MP3 player Normal bulb Energy saving Bulb Washing machine Shower Drill Electric Drill

9. 3 – 3 – 1 Summarise today’s topic in 5 sentences. Identify 5 key words. Now to 1 word. (with as many variations as there are numbers!) Back to Plenaries