1. 11.4 The Rate at Which Energy is Used

2. We use electrical power every day in many different ways. What is power? Power is how rapidly an appliance uses up electrical energy. Different electrical loads use different amounts of power Ex. A 300w bulb uses up 3 times as much electrical energy as a 100w bulb. The Rate at Which Energy is Used

3. Calculating Power We can calculate how much power a device uses with a simple equation. The symbol for electrical power is P. The unit for power is the watt (W). Power = Voltage Drop x Current P= V x I

4. PVIPVI The Power Triangle Just like with Ohms Law, we can use a triangle to help us remember the different formulae we need. P = V x I V = P I I = P V

5. Calculate the power of a vacuum cleaner if the operating voltage is 120v, and the current flowing through it when it is used is 7.90A. P= ? W V= 120V I= 7.90A P = V x I P = 120V x 7.9A P = 948 W The power used by the vacuum cleaner is 948W

6. Calculate the voltage of a computer that has 600W of power and 1.9A flowing into the monitor. P = 600W V = ? I = 1.9A V = P I V = 600W 1.9A V = 316V The voltage would be 316V.