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Equation for charge?
- It is the flow of electrons
Equation for current?
- It is the rate of flow of charge
Equation for voltage/potential difference?
- It is the work done per unit charge 1J/c
Equation for energy?
- measured in joules
Equation for power?
- It is the change in energy over the change it time
Equation for resistance?
- units = ohms
- It is the impotence to the flow of charge
Equation for coils?
Equation for weight?
Equation for GPE?
Equation for kinetic energy?
Equation for work done?
- 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?
Eff=useful energy out/total energy in
What is amplitude, wavelength and frequency?
Wave speed equation?
wave speed(ms-1)=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
- (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.
- 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.
- acceleration=change in velocity/time
- distance-time graph grad=speed
- velocity-time graph grad=acceleration
- area under v-t graph = distance
- p=momentum (kg m/s)
- m=mass (kg)
- v= velocity (ms)
Changes in momentum
- F(N)=change in momentum (kgm/s)/time(s)
- A low level of radiation thats always there.
- Make sure to take this into account
- 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.