4.2.3B Electrical Power

What About Watts?

Power Law• Moving electrons (current) requires ENERGY

• How much energy gets used depends on:• Strength of push – VOLTAGE• Rate of flow – CURRENT

IVP R

VI

RIR

VIVP 2

2

• 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?

Example #1

P = IV

P = (12 V)(10 A)

P = 120 W

• A 100 watt light bulb is connected to a 120 volt power supply.– What amount of current must pass through the light bulb?

Example #2

P = IV

100 W = (120 V) I

I = 0.833 A

• A 2.0 ampere current passes through a circuit with a 300 ohm resistance.– What is the power generated in this circuit?

Example #3

P = I2 R

P = (2.0 A)2 (300 Ω)

P = 1200 W or 1.2 kW

End of 4.2.3B – PRACTICE