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Equation for charge?
 Q=It(s)
 It is the flow of electrons
 Q=coulombs

Equation for current?
 V=IR
 I=V/R
 I=amps
 It is the rate of flow of charge

Equation for voltage/potential difference?
 V=IR
 V=volts
 It is the work done per unit charge 1J/c

Equation for energy?
 E=QV
 E=ItV
 E=energy
 measured in joules

Equation for power?
 P=IV
 P=E/T
 P=I²R
 P=V²/R
 P=watts
 It is the change in energy over the change it time

Equation for resistance?
 V=IR
 R=resistance
 units = ohms
 It is the impotence to the flow of charge

Equation for coils?
n1/n2=V1/V2


Equation for weight?
W=mg

Equation for GPE?
GPE=mg∧h

Equation for kinetic energy?

Equation for work done?
E=Fd


Circuit symbols
 Current flows from big stick of cell to little stick.
 A diode monitors the direction of flow.
 Transformers are used to step up or down voltage.

What types of radiation are there?
alpha, beta, gamma

How far does radiation travel?
 alpha= up to 10cm, highly ionising, blocked by paper
 beta= up to 1m, mid ionising, blocked by aluminium
 gamma=infinity, least ionizing, blocked by thick lead

What are the masses of different radiation?
 alpha= mass of 4, 2 protons and 2 neutrons
 beta= mass of 0, charge of 1
 gamma= nothing, nucleus just changes from high energy to low energy

What is half life?
The average time taken for half the isotopes/number of nuclei to decay

Equation for density?
density=mass/volume

Efficiency?
Eff=useful energy out/total energy in

What is amplitude, wavelength and frequency?

Wave speed equation?
wave speed(ms1)=wavelength(m) x frequency(Hz)

Series and parallel circuits

Rules for cells in circuits.
 When cells connected in series, total voltage = sum of individual voltages.
 When cells connected in parallel, total voltage = voltage of just one cell.

Rules for resistors in circuits.
 When resistors in series, resistance is added up.
 When resistance in parallel, the total resistance is less than of an individual resistor.
 Resistors always have same resistance, unless temperature is changed.

Calculating resistance in parallel.
 Method 1 3+ resistors
 Rt = total resistance
 Method 2 2 resistors
 resistance=product/sum
 (two R multiplied/two R added)
 Method 3 any number of identical resistors
 resistance of a single one ÷ total num of resistors.

Current in circuits.
 In a parallel circuit, current splits.
 In a series circuit, current is constant.

Voltage in circuits.
 In series, total voltage supplied is divided between components.
 Ratio of voltage = ratio of resistance
 In parallel,voltage supplied is the same in each component.

Short circuits
 Charge prefers the path with least resistance.
 Current will prefer to flow through a wire rather than a bulb if given the option.

Equations for speed and acceleration.
 speed=distance/time
 acceleration=change in velocity/time
 distancetime graph grad=speed
 velocitytime graph grad=acceleration
 area under vt graph = distance


Momentum equation?
 p=mv
 p=momentum (kg m/s)
 m=mass (kg)
 v= velocity (ms)

Changes in momentum
 F(N)=change in momentum (kgm/s)/time(s)
 F=mvmu/t

Background radiation
 A low level of radiation thats always there.
 Make sure to take this into account

Refraction
 When light is refracted, its wavelength changes, but frequency stays the same.
 Refraction is the bending of a wave when it enters a medium with different speed.
 When light travels into denser material=bends towards the normal
 When light travels into less dense material=bends away from the normal
 Light of a lower wavelength gets refracted more than light of a higher wavelength.

