Power Appliance transformation/W Oven 3000 Dishwasher 1400 Iron 1100 Hair Dyer 1500 Microwave 1000 TV 250 Stereo 60 Filament Lamp 100 Energy Saving Lamp 11 Drill 750 Fridge 1400 Worked examples What is the power of a television which transforms 0.5 MJ of energy in 1 hour? P = ? P = E/t E = 0.5 MJ P = 0.5×106 /3600 t = 1 × 60 × 60 = 3600 s P = 139 W A 1500 W hairdryer is used for 5 minutes, how much energy is transformed? P = 1500W P = E/t t = 5 x 60 = 300 s 1500 = E/300 E = ? E = 1500 × 300 E = 450000 E = 450 kJ Power, Current and Potential Difference We can also relate power to current and potential difference. Potential difference is the amount of energy supplied per coulomb of charge supplied as the charge passes the power source (remember, 1 V = 1 J/C). Current is the amount of charge per second. If we multiply the potential difference across a circuit by the current through it we have:
Appliance Power transformation/W Oven 3000 Dishwasher 1400 Iron 1100 Hair Dyer 1500 Microwave 1000 TV 250 Stereo 60 Filament Lamp 100 Energy Saving Lamp 11 Drill 750 Fridge 1400 Worked examples What is the power of a television which transforms 0.5 MJ of energy in 1 hour? P E t = ? = 0.5 MJ = 1 × 60 × 60 = 3600 s P = P = P = E/t 0.5×106 /3600 139 W A 1500 W hairdryer is used for 5 minutes, how much energy is transformed? P t E = 1500W = 5 x 60 = 300 s = ? P = 1500 = E = E = E = E/t E/300 1500 × 300 450000 450 kJ Power, Current and Potential Difference We can also relate power to current and potential difference. Potential difference is the amount of energy supplied per coulomb of charge supplied as the charge passes the power source (remember, 1 V = 1 J/C). Current is the amount of charge per second. If we multiply the potential difference across a circuit by the current through it we have: