AP Physics C E and M Review Cards

Q

Charge

Q units

Coulombs

Coulomb’s law

KqQ/r²

Q positive

E and F parallel

Q negative

E and F opposite

Net electric field

Add all electric fields

Voltage also

Potential difference

V net

Add all v

Along equipotential lines

Constant potential

Work required to move charge on equipotential line

0

Direction of equipotential lines

Perpendicular to force and field

Direction of movement that uses work

Same direction as force

Closer equipotential lines

Greater field

Electric flux

Electric field through surface

Outward flux

Positive

Inward flux

Negative

Flux from charges outside surface

0

Flux is proportional to

Charge enclosed

E field lines begin at

Positive charges

E field lines end at

Negative charges

E field at center of sphere

0

E field between center and radius

Increases linearly

Maximum e field at

Surface of sphere

E field outside of sphere

Decreases exponentially

Property of metals/conductors

Charge can move freely

E field in conductor

0

Any Gaussian surface completely inside a conductor encloses a net charge of

0

Electric flux through Gaussian surface completely inside conductor

0

On a conductor charge can only exist on

The surface

Net charge on conductor

Sum of charge on surface

E field on a metal

Constant

Potential difference on a conductor

0

E field outside of charged sphere equation

Kq/r²

E field at center of ring of charge

0

Acceleration due to electric field

QE/m

Change in speed due to potential difference

½ m(vf-vi)²

Unit of current

Amperes

Conventional current flows from

High to low potential

Conventional current is movement of

Positive charges

Resistance units

Ohms

Ohmic resistors

Obeys ohms law

Graph of I(V)

Straight line

Graph of I(R)

1/x

Resistors use

Current

Series circuit I net=

Equal I

Potential across wire

Constant

Current entering intersection =

Current leaving intersection

Connect voltmeter in

Parallel

Resistance of voltmeter

High

Connect ammeter in

Series

Resistance of ammeter

Low

Use Kirchhoff’s laws when

More than one battery

Node rule

Current entering intersection equals current leaving

Loop rule

Total potential differences around closed loop must be 0

Charge on capacitor plates are

Equal and opposite

Capacitance units

Farads

Voltage between capacitor plates

Constant

Energy stored in capacitor equals

Energy required to charge it

Adding more charge to a capacitor does what to the voltage

Increases it

Adding a dielectric affects energy by

Decreasing energy stored

Adding a dielectric affects capacitance by

Increasing it

Dielectric affects electric field by

Doesn’t change field

Dielectric affects charge by

Increasing it

As capacitor discharges the charge across it

Decreases

Charge across discharged capacitor will eventually be

0

At t=0 charge and voltage across capacitor is

0

Current across capacitor

Decreases with time

Increasing distance between capacitor plates will

Decrease capacitance

Time constant RC circuit

RC

Magnetic field units

Teslas

Magnetic force on a charge at rest

0

Magnetic force on charge is 0 when charge is moving

Parallel to field

Radius of charged particle path due to centripetal force in magnetic field

mv/qB

Force of a straight wire in a constant magnetic field

IlBsintheta

Wires with same direction of current

Attract

Wires with opposite direction of current

Repel

Torque in section of loop parallel to field

0

Magnetic flux units

Webster

Direction of induced emf

opposite of change

Current in circuit with inductor immediately after closing loop

0

After a long time the inductor acts like a

Wire

Time constant for LR circuit

L/r

Work

Change in energy

Circle

Out of page

X

Into page

E field due to sphere of uniformly distributed charge

Kq/a²

E inside sphere

0

E field due to non uniform line of charge

Integral of kbxdx/(L+a-x)²

E field due to uniform arc of charge

1/2pie(lambda/R)sintheta

E field due to uniformly charged sphere inside sphere

Kqr/R³

E field due to uniform line of charge

Kq/(a(l+a))

Voltage across cylindrical capacitor

2kq/L(ln(b/a))

Loop and current same direction

V=-IR

Loop and current opposite directions

V=IR

Loop exits positive terminal of battery

Add V

Loop exits negative terminal of battery

Subtract V

Charge on capacitor

Cv(1-e^(-t/RC))

Discharging a capacitor

Qe^(-t/RC)

Magnetic field around wire

muI/2pir

V for bar moving in B field

-Bhv