AP Physics 2: Unit 11 Circuits

Current definition

Q/t

-is directed out of the + terminal, into the - terminal

Which direction does current flow?

To be in the direction of positive charge flow (opposite direction of e-)

Ohm’s Law

V = IR

(V is voltage drop across resistor, I is current through resistor, R is resistance)

-V is NOT ALWAYS voltage of battery

Ohmic vs. Non-Ohmic

Ohmic - constant resistance, regardless of current

Non-Ohmic - change their resistance depending on current/voltage

P

q/t, energy being dissipated

IV

TWO VERSIONS OF POWER THAT ARE NOT ON FORMULA SHEET

P = I²R

P = V²/R

What is P=IV for?

For battery, gives power supplied by circuit

Capacitors

C = Q/V ,how well a capacitor can store charge

Capacitors store energy also, given by

½ QV = ½ CV²

Series

Same I FOR RESISTORS

SAME Q FOR CAPACITORS

Parallel

Same V

Q =

CV

Each resistor gets a different amount of current if in parallel

I tot = I1 + I2

I1 = Itotal (R2/R1+R2)

I2 = Itotal (R1/R1+R2)

TO FIND HOW MUCH OF CURRENT BOTH RESISTORS GET

Capacitor makes it so no current

flow through the leg of the circuit

Voltage drop across resistor parallel to a capactor

can allow you to input in Q=CV

VC = Q

Kirchoff’s Rule

I in = I out

Loop Rule

SUM OF V = 0

Current and resistors

Same direction as current -

opposite direction of current IR

Terminal voltage

Vab = EMF - IR

Ammeter

MEASURES CURRENT
no resistence - to not change current

IN SERIES

Voltmeter

In parallel

R = infinite - to not draw current away

MEASURES VOLTAGE CHANGE

When asked what something is when theres a change and a constant…

Find an equation that gives both the said constant and the answer

In polarized solutions

Negative and positive ions move, electrons cannot

7-8

I= V/Rtotal, overall constant

Energy dissipated is

POWER

*Big, important concept!

When charging, a capacitor will act like ideal wire immediately after being included in a circuit, but will act like a switch after becoming charged

When discharging, a capacitor will act like an ideal battery immediately after being included in a circuit, but will act like dead battery after fully discharging