#AP Physics C: E&M - Unit 3: Circuits - The Night Before ⚡

Hey! Let's get you prepped for the exam with a high-impact review of circuits. This is your go-to guide for a confident test day. Let's make it click!

#3.0: Circuit Overview 🌐

Unit 3 focuses on connecting electrical devices, analyzing current flow, and understanding power and potential differences in circuits. It is a high-value topic, making up 17-23% of the AP exam. This unit is crucial for understanding how electrical components interact. Remember to review your AP Physics 1 notes on circuits if you need a refresher!

#3.1: Circuit Quantities 🔋

#Voltage, Current, and Resistance: The Big Three

Remember from Unit 1, voltage is work per unit charge. Now, let's add current and resistance to the mix. Think of it like water flowing through a hose:

• Voltage (V): Water pressure 💧

• Current (I): Amount of water flowing 💨

• Resistance (R): Clogs or obstructions in the hose 🚧

Image from freeingenergy.com

#Current (I) 💨

Current is the rate of charge flow, measured in Amperes (A). The equation is:

$$I = \frac{dQ}{dt}$$

Where:

• I is current (Amps)

• Q is charge (Coulombs)

• t is time (seconds)

#Microscopic View of Current

Current is also related to the drift velocity (v_d) of charge carriers. Imagine electrons slowly drifting through a wire, not zooming!

Image from openstax.org

The equation linking current to drift velocity is:

$$I = nAv_dq$$

Where:

• n is the number of charge carriers per unit volume
• A is the cross-sectional area of the wire
• v_d is the drift velocity
• q is the charge of each carrier

#Current D...