Physics Flashcards
What are the energy stores
Nuclear
Thermal
Magnetism
Kinetic
Gravitational potential
Elastics potential
Chemical
Electrostatic
What do Vectors have
Magnitude and direction
What do scalars have
Magnitude
formula for specific heat capacity
change in thermal energy / change in temp * mass
what is power
the rate of energy transfer or doing work
how do you calculate power
energy transferred/time
what is conduction
The process in which vibrating particles transfer energy
what is the formula for charge
current*time
what is the voltage of the uk mains supply
230v
what is AC current
when the current is constantly changing directions
what type of current does the mains supply supply
AC
what type of current does a battery supply
DC
what is DC current
current that is always flowing in the same direction
what are the three wires cables have
neutral
live
earth
What is the job of the neutral wire
completes circuit
what is the job of the Earth wire
protecting wiring- safety- stops appliance casing from becoming live
What is the Job of the live wire
provides the alternating potential difference
What is the colour of the live wire
brown
what is the colour of the Earth wire
yellow and green
what is the colour of the neutral wire
blue
What is specific heat capacity
Specific heat capacity is the amount of energy needed to raise the temperature of a kg of a substance by 1 degrees
What is conduction
the process in which vibrating particles transfer energy to neighbouring particles.
What is Convection
the process in which energetic particles move from hotter to cooler regions
Positives of wind power
minimum maintenance costs
no pollution
no fuel costs
no permanent damage to landscape
Negatives of Wind power
not reliable
high start up costs
not reliable
eye sore
Positives of Solar cells
running costs very small
no pollution
Negatives of solar cells
high start up costs
What is Current
Current is the flow electricity
What is potential difference
driving force that pushes the current around measured in volts
What is resistance
anything in the circuit which slows the flow of electricity down
What resistance do ohmic conductors have
constant resistance
What does it mean if an ohmic conductor has constant resistance
the resistance doesn’t change with the current so at a constant temp current flowing through an ohmic conductor is directly proportional to the potential difference across it
What position must Ammeters be in to measure amps
Series
What position must voltmeters be in to measure Potential difference
Parallel
What are light dependent resistors
a resistor that dependent on the intensity of the light
in darkness resistance is highest
in bright light resistance falls
What are Thermistors
a temperature dependent resistor
in hot conditions the resistance falls
in cool conditions resistance increases
What are the qualities of a series circuit
the different components are connected in a line end to end
if one thing is disconnected the whole circuit fails
if all cells in a series circuit are connected and are the same way their potential difference adds up
Resistance adds up
current is the same everywhere
What happens to the total potential difference in a series circuit
the total potential difference is shared between all components in circuit
What happens to the potential difference of two cells when they are connected in the same direction in series
the potential difference is added up
In series circuits how do you get the total resistance
you add the resistances of all the components in the series circuit
What happens when you add resistors in series
it increases the resistance of the circuit
What happens when you add resistors in parallel
total current of circuit increases while total resistance decreases
What is the relationship between current resistance and voltage
As long as resistance stays constant and voltage increases current should increase proportionally
Why do filament lamps graphs look like that
as wire heats up it produces light.
When wire gets hotter there is more resistance. When there is more resistance there is less steep of a curve
Why are diodes able to cause current to flow in only one direction
diode- device that only allows current to flow in one direction- does this by having high resistance in opposite direction
What are diodes
devices that cause current to flow in one direction
What is the function of a circuit breaker
breaks if to much current flows through a circuit
What is the function of a diode
only allows current to flow in one direction
What is the function of a light emitting diode
emits light if current flows through it in a certain direction
What is the function of a fixed resistor
to provide a fixed amount of resistance in ohms
What is the function of a variable resistor
to provide an easily changeable resistance
What is a light dependent resistor
a resistor where resistance decreases when light intensity increases
What is the function of a thermistor
as the temperature increases the resistance decreases
How much energy does a power station produce
The amount of energy a power station produces is based on demand so it varies
When does energy demand peak
Late afternoon or evening
How do power stations deal with surges in demand for electricity
Power stations deal with surges in demand by working well under maximum capacity as they need to have spare capacity when dealing with surges
What happens when lots of current is transmitted through a wire
Most of the energy is wasted and transmitted to the surroundings through heat
How does the national grid minimalize energy loss
It transmits low amounts of current with high voltage
What is the role of step up transformers in the national grid
They increase the voltage to around 400000 volts while also decreasing the current
What is the role of pylons in the national grid
Supports the electrical cables that transmit the current and voltage
What is the role of wires in the national grid
wires transmit current in the national grid
What is the role of step down transformers in the national grid
They reduce the voltage back down to 230 volts and increase the current
Why is it important to reduce voltage before it reaches towns and cities
High voltage is dangerous
Will blow appliances apart
What is the UK main supply Hz
50
What is Hz
how many times the ac current fluctuates between positive and negative a second
Where do we find D.C. current
in cells and batteries
What is the function of Oscilloscopes
They create P.D time graphs
What is a common problem that happens in a circuit
Sudden increases in current (surges)
When do surges usually happen
When you turn your appliance on or off or there is a fault in the circuit or appliance
What problems do surges create
Can damage appliances
cause fires
cause electric shocks
What are some safety precautions of surges
Fuses
Earth wires
Double insulation
Circuit breakers
How do fuses and circuit breakers stop surges
They break the circuit whenever the current gets too high
What is a fuse
A thin piece of wire that is connected to the live wire
How does a fuse break a circuit
When a surge goes through the live wire it will go through the fuse
the fuse will melt due to the surge thus breaking the circuit
Adv of fuse
They are simple
They are cheap
Disadv of Fuses
Permanently broken after single surge
How do Circuit breakers break a circuit
When a surge goes through the circuit breaker the circuit breaker gets tripped thus turning off the entire circuit
Adv of Circuit breakers
Circuit breakers are not broken after single use
Disadv of circuit breakers
They are more expensive than fuses
How does Earthing stop electric shocks
Earth wire diverts current and gives it an alternative pathway instead of going through casing
How does double insulating stop electric shocks
if you cover the device in a non-conductive material the current wont go into the casing and give you an electric shock.
You then wont normally need an earth wire
What are the risks of using radiation
Ionising radiation- ionise atoms in living cells- may damage them (leads to cancer) or kill them off completely
What is exposure to radiation called
Irradiation
How are alpha sources of radiation dangerous in the body
Inside the body, alpha sources can cause damage in a localised area, so contamination is the main concern when working with alpha source
What is contamination
When unwanted radioactive atoms get on or into an object
Why is contamination dangerous
If the radioactive atoms get into the body they can then decay releasing radiation harming the body
Why are beta and gamma sources less damaging inside the body
they are more likely to pass through a cell than to be absorbed
Why are Gamma sources the least dangerous inside the body
They mostly pass straight out of the body as they have the lowest ionising power
Why are beta and gamma sources dangerous outside the body
The beta and gamma sources can penetrate the body and get into the vital organs
Why are alpha particles less dangerous outside the body
Alpha particles can’t penetrate the skin and are easily blocked by a small air gap
What is half-life
The time taken for the number of radioactive nuclei in an isotope to halve
How many protons and neutrons is an alpha particle made out of
An alpha particle is made of 2 protons and 2 neutrons
How are nuclear equations written out
Atom before decay —-》atom after decay + radiation emitted
What happens in an atom when beta decay occurs
A neutron in the nucleus turns into a proton while a fast-moving electron (beta particle) is released
What happens to the atomic mass when beta decay occurs
The atomic mass doesn’t change as a proton and a neutron have the same value of mass
What happens to the charge of the atom when beta decay occurs
Since the protons in the nucleus have increased by 1, the charge of the atom will also positively increase
What happens to the atomic number of the atom when beta decay occurs
Since the atomic number is dependent on the number of protons, the atomic number will increase as during beta decay, the number of protons increase
How can the distance at which electrons orbit the nucleus change
If electrons absorb EM radiation, they move to a higher energy level, which is further away from the nucleus
If they release EM radiation, they move to a lower energy level that is closer to the nucleoside
