IB Physics HL Topic 5- Electricity & Magnetism

Energy

the ability to do work (J),
always conserved

work done

Wd=Fscos(ß)
force*distance moved in direction of force

Gravitational potential energy

the energy and object has due to its position- in particular height from a given point

Weight

W=mg

Ep

Ep=mgh

Ek

Ek=1/2mv^2

Power

a measure of how fast energy is transferred or transformed,
the rate of doing wrk

P

P(W)=W/t
P=Fv

Current

rate of flow of charge (Ampere),
takes the path of least resistance

Resistance

something which resists an electric current

Electroscope

device which detects and measures electric fields

Voltage

(Potential difference) the amount of push given to the e-

Series

Vt=V1+V2
It=I1+I2
Rt=R1+R2

Parallel

Vt=V1=V2
It=I1+I2
1/Rt=1/R1+1/R2

Voltmeter

measures potential difference in Volts,
always connected in parallel,
high resistance

Ammeter

measures Current in Amps,
always connected in Series,
low resistance

Qe

charge of an e-=1.6*10^-19

Charge units

measured in Coulombs

Kirchoff's first law

the sum of the currents leaving a point is the same as the sum of the currents entering that point

charge carrier density

n, the number of charge carriers per volume

drift speed

the speed with which e- move down a wire

Charge which passes every second

I=nAQV
A=cross-sectional area of wire

Resistivity

Resistance=resistivity(rho)*length/cross-sectional area
measured in Ohm meters

Electric field

a region around a charge where another charge will experience a force

Voltage, work done, charge

Wd=QV

Power, work done, time

Wd=Pt

Power, current , voltage

P=IV

Power, Voltage, Resistance

P=I^2V

Magnetic field

zone around a magnet in which a magnetic object experiences a force

Fleming's left hand rule

ThuMb - Motion, First Finger - Field, SeCond finger - Current

Electromotive force

force provided by power supplies which pushes the current around a circuit,
the total work done by a power supply per coulomb of charge

Kirchhoff's 2nd Law

around any closed loop, the sum of the emfs is equal to the sum of the pds

Internal resistance

the resistance (r) which is provided by the power source itself,
source of lost volts

Emf

Emf=pd + lost volts,
E=Ir+IR

Potential dividers

a potential divider is used to output a different voltage to that supplied by the power source
Two resistors connected in series such that a fraction of the total voltage may be tapped off by connecting across one of the resistors

Potential divider equation

Vout=Vin * R2/(R1+R2)
R1/R2=V1/V2

Electric field strength equation

uniform:
F=QV/d
F=EQ
E=-V/d
radial:
E=kQq/d^2

Magnetic flux density

The amount of the magnetic flux in a unit area perpendicular to the direction of the magnetic flow.
F=BILsin(ß),
a magnetic flux density of 1Tesla produces a force of 1N on a 1m long wire with a current of 1A

Magnetic force on a moving charge

F=qvBsin(ß)