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What About Watts? 4.2.3B Electrical Power Power Law • Moving electrons (current) requires ENERGY • How much energy gets used depends on: • Strength of push – VOLTAGE • Rate of flow – CURRENT V2 PI VIV 2 P IV R I R R Example #1 • A 12 volt battery is connected to a circuit which allows 10 amperes of current to flow. – What is the power output of this circuit? P = IV P = (12 V)(10 A) P = 120 W Example #2 • A 100 watt light bulb is connected to a 120 volt power supply. – What amount of current must pass through the light bulb? P = IV 100 W = (120 V) I I = 0.833 A Example #3 • A 2.0 ampere current passes through a circuit with a 300 ohm resistance. – What is the power generated in this circuit? P = I2 R P = (2.0 A)2 (300 Ω) P = 1200 W or 1.2 kW End of 4.2.3B – PRACTICE