EOY exam Flashcards
what is the weight equation?
weight = mass x gravitational field strength (N) = (Kg) x (N/Kg)
what is the work done and power equation?
work done = force x direction
E = f x d
(J) = (N) x (m)
what is the power equation?
power = work done ÷ time taken
what is the potential difference equation?
V = I x R potential difference (volts) = current x resistance volts = amps x ohms
what is the pressure and pressure in a fluid equation?
pressure = force ÷ area
pressure (pascals)
pressure in a liquid = heigh/depth of column x density x gravitational field strength
P = h x ρ x g
pascals = m x kg/m3 x n/kg
what is the gravitational potential equation?
GPE = M x G x H
Gravitational potential energy = mass x gravitational field strength x height
(J) = (Kg) x (N/Kg) x (m)
what is the kinetic energy equation?
KE = 1/2 x mass x speed KE = 1/2 x m x v2 (J) = 1/2 x (m) x (m/s)
what is the specific heat capacity equation?
ΔQ = m x c x Δ ϴ
energy change = mass x specific heat capacity x temperature change
(J) = (Kg) x (J/Kg/degrees) x degrees
what is the specific latent heat equation?
Q = M x L
thermal energy = mass x specific latent heat
(J) = (Kg) x (J/Kg)
what is the charge equation?
Q = I x T charge = current x time
what is the force on a conductor equation?
F = B x I x L
force x magnetic flux density x current x length
what is specific latent heat and specific heat capacity?
SLH: the amount of energy required to change the state of 1Kg of substance
SHC: the amount of energy needed to raise the temperature of 1kg of substance by 1 degree
what is current ?
the flow of electrical charge around a circuit. Current will only flow through an electrical component if there is a potential difference across that component and if the circuit is complete.
what is potential difference?
(voltage) is the driving force that pushes charge around a circuit
the energy transferred per columb of charge that passes between two points
what is resistance?
anything that slows down the flow of charge
link potential difference, current and resistance?
the higher the potential difference across a given component, the higher the current will be
the greater the resistance of a component, the smaller the current flowing through it
what is the energy transferred equation?
energy transferred = charge moved x potential difference
E = Q x V
why does resistance increase with temperature?
when electrical charge flows through a component it has to do work against resistance causing an electrical transfer of energy.
Some of this energy is dissipated to the thermal energy stores of components and the surroundings so when a current flows through a resistor it heats up.
This happens because the electrons collide with the ions in the lattice that make up the resistor as they flow through it giving the ions energy to vibrate and heat up.
The more the ions vibrate, the harder it is for electrons to get through the resistor because there is more collisions. For a given pd the current decreases as the resistor heats up.
how can you reduce the amount of energy dissipated to thermal stores as the current flows between components
use low resistance wires
explain the energy transfers in a kettle?
electrically from the mains ac supply to the thermal energy store of heating inside the kettle
the higher the current…
the more energy is transferred to the thermal energy stores of the components
what are the negatives of heating in a circuit?
efficiency reduced because less energy is transferred to useful and more is transferred to it’s thermal energy stores
if temp gets too high the fuse can melt and break the circuit
what are the advantages to heating in a circuit?
toasters contain a coil of wire with a high resistance and when a current passes through it its temp increases and it glows red and gives off infrared radiation heating your bread
what does power transferred depend on?
pd and current
the pd tells you how much energy each unit of charge transfers
current tells you how much charge passes per unit of charge
how do you calculate power if you aren’t given the pd?
P = I SQUARED X R POWER = CURRENT SQUARED X RESISTANCE
what is static electricity?
the build up of electrons and charge as a result of friction