not assessed paper 1 Flashcards
what is internal energy?
the energy stored by the particles that make up a system - the total energy that its particles have in their kinetic and potential energy stores
what is latent heat?
the energy needed to change the state of a substance
what is specific latent heat?
the energy needed to change the state of 1kg of a substance without changing the temperature
what is the specific latent heat for changing between a solid and a liquid (melting or freezing) called?
the specific latent heat of fusion
what is the specific latent heat for changing between a liquid and a gas called?
the specific latent heat of vaporisation
what is the formula for specific latent heat?
energy = mass x specific latent heat
E = mL
what is the unit for specific latent heat?
J/kg
What is alternating current and give an example.
An electrical current where the current is constantly changing direction. It is used in mains electricity.
What is the voltage and frequency of the mains electricity current?
230 v
50 Hz
What is direct current and give an example.
Current that is always flowing in the same direction. Cells and batteries supply direct current.
in a series circuit is potential difference shared or kept the same
the total pd of the supply is shared between the various components. the potential differences round a series circuit always add up to equal the source pd
in a series circuit is current shared or kept the same?
kept the same - the same current flows through all components
what is the size of the current in a series circuit determined by
the total pd of the cells and the total resistance of the circuit i.e. I = V / R
how do you calculate the total resistance of two components in a series circuit?
by finding the sum of the two components - when you add a resistor in series the two resistors have to share the total pd
if you add more resistors in series does the current increase or decrease across them? why?
decrease - it means the pd across each resistor is lower, so the current through each resistor is also lower. In a series circuit, the current is the same everywhere so the total current in the circuit is reduced when a new resistor is added. This means the total resistance of the circuit increases.
what happens if more cells are connected the same way in a series circuit?
their potential differences add together
in parallel circuits is the potential difference shared or kept the same across components?
kept the same - all components get the full source pd
would identical bulbs connected in parallel be the same or different brightnesses?
the same
in a parallel circuit is current kept the same or shared?
shared between branches
what is the total current in a parallel circuit equal to?
the total of all the currents through the separate components
does adding a resistor in parallel increase or reduce the total resistance
reduce
if you have two resistors in parallel, is their total resistance more than or less than the resistance of the smallest component
less than
what is alternating current produced by?
alternating voltages - voltages where the positive and negative ends keep alternating
what is direct current created by?
direct voltage
how many cables are most electrical appliances connected to the mains supply by?
three-core cables
what colour is the neutral wire?
blue
what is the purpose of the neutral wire?
the neutral wire completes the circuit - when the appliance is operating normally, current flows through the live and neutral wires. It is around 0 V.
what colour is the live wire?
brown
what is the purpose of the live wire?
the live wire provides the alternating potential difference (at about 230V) from the mains supply
what colour is the earth wire?
green and yellow
what is the purpose of the earth wire?
it is for protecting the wiring, and for safety - it stops the appliance casing from becoming live. It doesn’t usually carry a current - only when there’s a fault. It’s also at 0 V
which wire can give you an electric shock?
the live wire
