Electrical energy How much work can electricity do?
What we are going to do today What is potential difference? How do we transfer energy from one form to another? What is the formula for electrical energy ? Experiment, electrical energy to thermal energy Reviewing your results
Potential Difference (p.d.) Potential difference is another name for voltage Think of it like a ski-slope At the top of the slope you have lots of potential energy which you convert to kinetic energy. The battery gives a potential difference which allows you to covert the electrical energy into light energy in a bulb. The definition of the volt is work done per coulomb of charge transferred between two points.
The human power pack Voltage + - resistor battery
Write down three energy changes from electrical to another form of energy Electrical energy --------- energy Toaster heat Think about the electrical goods around your bedroom
The formula for electrical energy E = ItV E = Energy I = Current t = Time V = Voltage
We are going to use this formula to see how much energy is needed to heat up a piece of metal 10V + - heater A V E = ItV
The Experiment Take a measurement after every 3 degrees Draw a graph of temperature against energy (use a computer) Temperature Energy How many joules of energy were needed to raise the temperature by one degree? Temperature Time (s) Current I Voltage V Energy E=ItV 3 6 9 12 15 18
Power Electrical power is like power found earlier Power = work/time Work = Force x Distance Work = ItV Power = IV Electrical formulas What power would you need to heat your block up by 10 degrees in 5 minutes? Power is measured in Watts