Announcement Ohm’s law video is due at midnight Makeup lab today No lab tomorrow

Why Make Electrons Flow Anyway? 4.2.3A Ohm’s Law & Circuit Basics

Ohm’s Law Voltage results in current flow More voltage = more current Resistance opposes current flow More resistance = less current

Example #1 A potential difference of 25.0 volts is supplied to a circuit with 100 ohms of resistance. How much current flows through this circuit? I = V / R I = 25.0 V / 100 Ω I = 0.25 A

Example #2 A current of 2.0 amperes flows through a 10 ohm resistance. What voltage must be applied to this resistance? I = V / R V = IR V = (2.0 A)(10 Ω) V = 20 V

Example #3 A 10 volt battery establishes a current of 5.0 amperes in a circuit. What is the resistance of this circuit? I = V / R R = V / I R = (10 A) / (5.0 A) R = 2.0 Ω

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

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