general Physics Flashcards
gcse study
what is the equation for thermal heat capacity(energy for change of state)
thermal capacity=mass×specific heat capacity
Definition of latent heat
The energy transferred when a substance changes state is called latent heat (without change of temperature)
definition of specific latent heat
the energy required to change the state of 1kg of a substance with no change in temperature
definition of specific latent heat of fusion
the energy required to change the state of 1kg of a substance from solid to liquid with no change in temperature
definition of specific latent heat of vaporisation
the energy required to evaporate 1kg of a substance with no change in temperature
what is an electric current and what are its properties
An electric current is the flow (movement) of electric charges.
Electric current is measured in amperes (A)
A current has the same value at every point in a single closed loop(series circuit), in parallel the current splits with different branches then combines again before it goes back into the supply
An ammeter measures the flow of current that passes through it,
ammeters have to be connected in series with the electrical component
what is potential difference
Potential difference is the difference in the amount of energy that charge carriers have between two points in a circuit
Potential difference (p.d.) is measured in volts (V) and is also called voltage.
A potential difference of 1 volt will transfer 1 joule of energy to a component per every coulomb of charge,
The energy is transferred to the electrical components in a circuit when the charge carriers pass through them.
We use a voltmeter to measure potential difference (or voltage), Voltmeters measure the potential difference (voltage) between two points in a circuit. For example between two points either side of a component above it.
Voltmeters must always be connected in parallel
what is resistance and what happens to the current if resistance increases and what happens to the current if potential difference increases
Resistance is the force that counter acts the flow of current and it is measured in ohms, Ω.
When charge flows in an electric circuit, the size of the current is affected by two things:
The resistance: If the resistance is increased, the current will decrease.
The potential difference: If the potential difference is increased the current will increase.
in an ohmic conductor the resistance remains constant
The combined resistance of two resistors in parallel is less than the resistance of either of the two resistors by themselves
what are diodes
A diode is a component that only allows current to flow through it in one direction
A rectifier is a component that turns an alternating current (repeatedly changes direction) into a direct current (one direction) diodes act as a rectifier
what are thermistors
A thermistor is a component where resistance changes with its temperature.
Usually, increasing temperature decreases the resistance.
We can use a thermistor to turn a heater off when a house reaches certain temperatures.
what are (LDR)s
A light dependent resistor (LDR)s changes resistance when light intensity changes.
Usually, increasing light intensity decreases the resistance.
We can use LDRs to switch lights on when it gets dark or to know whether or not a camera phone needs to use “flash”
in series circuits what happens to the voltage and current
the current remains the same at all points in the circuit
and the voltage across each component is different, and the sum of all the component voltage is the total battery voltage
in a parallel circuit what happens to the current and the voltage
the current is split between each branch
and the voltage across each branch is the same
What is the equation for the resultant force
resultant force = mass x acceleration
what is hooks law
Hooke’s Law tells us that the extension of a spring is directly proportional to the force applied to the spring:
force =spring constant x extension
what atomic model did J.J Thompson discover and when
in 1897 J.J Thompson discovered electrons and created the plum pudding model, which was a ball of positive mass with negatively charged electrons
what atomic model did Ernest Rutherford discover and when
in 1909 Ernest Rutherford discovered alpha particles could bounce back off and pass through atoms he concluded that an atom’s mass is concentrated in the atom’s centre called the nucleus which contain positively charged protons
what atomic model did Niels Bohr discover and when
In 1913 Niels Bohr he also discovered that electrons orbit around the nucleus at fixed distances, all this created the modern atomic model
What atomic model did Jame Chadwick discover and when
In 1932 James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons, all this created the modern atomic model
What happens when an atom absorbs electromagnetic radiation
When atoms absorb electromagnetic radiation, electrons move to a higher energy level further away from the nucleus
what happens when an atom emits electromagnetic radiation
When atoms emit electromagnetic radiation, electrons can drop to a lower energy level, closer to the nucleus
What are Nuclides
A nuclide is a type of isotope.
A nuclide refers to a specific nucleus that contains a certain number of protons and neutrons.
A carbon nuclide with 6 protons and 6 neutrons is different to a carbon nuclide with 6 protons and 7 neutrons. However, both are isotopes of carbon.
name four types of radiation and what are they made of
Alpha radiation helium nuclei
Beta radiation electron
gamma radiation gamma rays
neutron
what is alpha radiation stopped by and how ionising is it
stopped by 5cm of air or a sheet of paper and it is very ionising the most out of all the types of radiation we learn in GCSE
what is beta radiation stopped by and how ionising is it
stopped by 2mm - 4mm of aluminium and it is very ionising medium ionising out of all the types of radiation we learn about in GCSE
what is Gamma radiation stopped by and how ionising is it
reduced by lead stopped by nothing and is the least ionising out of all the types of radiation we learn about at GCSE
What is the rule between the strength of radiation and the level of penetration it has
More strongly ionising radiation is less able to penetrate materials. It interacts with (damages) materials much more, so it comes to a stop sooner
how does nuclear fission happen
Nuclear fission splits 1 nucleus into 2 or more smaller nuclei. It usually happens in nuclear reactors.
A neutron collides with a large unstable nucleus and is absorbed.
This nucleus then splits into two daughter nuclei. This releases large amounts of energy and more neutrons. These neutrons can then collide with other nuclei resulting in a chain reaction.
The energy released can used to boil water, which rotates a turbine. The turbine then turns a generator, which produces electricity
how does nuclear fusion happen
Nuclear fusion fuses (joins) 2 smaller nuclei to create 1 larger nucleus. some mass is converted into energy and is transferred as radiation
what is half life
half-life is the average time taken for the number of radioactive nuclei to halve
name all the energy stores
magnetic.
internal (thermal)
chemical.
kinetic.
electrostatic.
elastic potential.
gravitational potential.
nuclear.
what is internal energy store
a internal energy store is the sum of kinetic energy stores and the potential energy stored in the chemical bonds
what does the area under the graph of a velocity time graph represent, also what does the gradient represent
The area under a velocity-time graph is equal to the distance travelled by an object to find the area under the graph break it down into small shapes and add the areas of the shapes, the gradient represents acceleration
what do we use levers and gears for?
We use levers and gears to transmit the rotational effect of a force from one place to another,
We can use levers to increase the distance between the pivot and where we’re applying the force,
Moment = force x distance so using a lever means we need to use less force to get the same moment,
We can use different sized gears to change the moment of the force.
For example, a force transferred to a larger gear wil have a larger moment.
This is because the distance to the pivot is greater.
what happens to waves when they travel from one medium to another
When waves travel from one medium to another their speed and wavelength change but their frequency stays the same,
this is because the source of the wave is producing the number of oscillations,
the speed and wavelength change together because they are directly proportional to each other, speed and wavelength change when the medium becomes denser
what are the four things a wave can do when it meets a boundary (the point where two mediums meet)
Waves can be reflected, refracted, absorbed and transmitted (passes through) at the boundary
how does reflection happen
Reflection happens when a wave hits a flat surface (plane) and bounces off, the law of reflection states that the angle of incident = the angle of reflection
what is refraction
A wave’s speed can change when moving from one medium to another.
If the wave crosses to the new medium at an angle (not 90 degrees), the change in the wave’s speed will cause the direction of the wave’s motion to change and the wave will appear to bend.
This is called refraction.
what is Transmission
transmission is when a wave carries on travelling through a new material.
This often leads to refraction.
what is absorption
When waves meet some materials, the energy is absorbed by the material,
For example when light falls on a matt black surface most of the energy is absorbed.
what is the normal in reflection
the normal is the point perpendicular to the plane(mirror)
what is the angle of incident in reflection
The angle of incidence is the angle between the incident (incoming) light ray and the normal.
what is the angle of reflection
The angle of reflection is the angle between the reflected light ray and the normal.
what is the law of reflection
angle of incident = angle of reflection
describe a sound wave
Sound waves are longitudinal waves. They can travel through solids by causing vibrations in the solid.
Sound is produced by the vibration of particles in a medium (the substance that waves travel through).
The vibrations mean that sound waves travel in a series of compressions (where the medium is squashed together) and rarefactions (where the medium is stretched apart).
what range of frequencies can humans hear
20hz - 20,000hz
what is ultra sound
anything above 20,000hz
what is the relationship between the rigidness of the medium and the speed of the sound wave traveling through it
the more ridged the substance the faster the sound wave will travel through the medium
what is the relationship between level of compressibility of the medium and the speed of the sound wave traveling through it
the more compressible the substance the slower the sound wave will travel through it
what are the four uses of ultra sound
Doctors use ultrasound to perform scans of a developing foetus, dog whistles have a frequency above 20,000hz which dogs can hear but humans can’t hear ,We can use echo sounding to detect objects in deep water and also to measure water depth, We can use ultrasound to find flaws in objects or materials (e.g. pipes or wood).
what two types of waves do earthquakes produce
P-waves (Primary waves) these are longitudinal seismic waves.
P-waves travel at different speeds through solids and liquids,
S-waves (Secondary) these are transverse seismic waves.
S-waves cannot travel through liquids (only through solids)
what happens to light if it enters an optically dense medium
light will slow down,
when light enters a more optically dense medium it is refracted closer to the normal.
what is the equation for wave frequency that uses number of oscillations and time
wavefreq = number of oscillations / time
what direction do transverse waves cause particles in a medium to vibrate
perpendicular to the direction of the waves motion
what direction do longitudinal waves cause particles in a medium to vibrate
A longitudinal wave causes the medium’s particles to vibrate parallel as the wave’s motion
explain how gamma radiation can be used in medicine
gamma-emitting tracers are injected or swallowed by a patient. Gamma sensitive sensors are used to create an image of where the tracers are, the half life of the tracers must be short enough so the patients radiation exposure is limited,
gamma radiation can also be used to sterilise medical equipment or to treat cancer cells in a process called radiotherapy, this is done because the radiation damages cells including cancer and bacteria cells
what direction does a magnetic field flow
From north to south pole
what are the four magnetic metals
Iron, steel, cobalt and nickel
what is a permanent magnet
A magnet that produces its own magnetic field
what is an induced magnet
A magnet that becomes magnetic when it is already in a magnetic field
what are the three ways of increasing the strength of an electromagnet
increase the number of coils
increase the current
add or change the core (soft metal like iron creates a stronger field)
what is a solenoid
a solenoid is a cylindrical coil of wire, this is done to the wire in order to increase the strength of a magnetic field by combining multiple magnetic fields (they are essentially electromagnets without the core)
what does each finger represent in Fleming’s left hand rule
your thumb is the motion the wire will turn, the index finger represents the magnetic field and it runs from north to south(the palm being north and the tip of the finger being south) and your middle finger is the direction of the current
what is a magnetic field
a magnetic field is an area around a magnetic in which other magnets or magnetic material will experience a force between itself and the magnet, the strength of a magnetic field line is the strongest at the poles, the closer together the field lines are the stronger the magnetic field
explain what is the motor effect and why is it created
the motor effect is the force experienced by a current carrying wire when it is placed in a magnetic field, this force on the wire is due to the interaction between the field created by the current carrying wire and the magnetic field, the magnet producing the magnetic field will experience an equal and opposite force, the direction of the force is reversed if the current is reversed or if the direction of the magnetic field is reversed
describe what a relay is, how it works in an electric circuit and why it is used
a relay is a separate low voltage circuit that contains an electromagnet which when turned on completes the the main higher voltage circuit, this is done in order to reduce the chance of electrocution
explain how electric motors work
a current flows through a loop circuit which is at a right angle to a magnetic field this causes the wire to start rotating, because of the motor effect, but once the circuit has rotated pasted 90 degrees the rotation will stop this is because the forces acting on the wire in the circuit are now pushing the circuit in the opposite direction causing it to remain stationary, this can be fixed by using a split ring communicator which will disconnect the circuit from the power supply and then reconnect the circuit when the direction of the current has switched
explain how a moving coil loud speaker works
we have a cone which has a coil of wire wrapped around one end, the coil of wire is connected to an alternating current, we also have a permanent magnet with one pole inside the wire and the over pole is surrounding the wire in a circular shape, the current creates a magnetic field, the field of the coil interacts with the permanent magnets magnetic field, these magnetic fields either attract or repel each other, this causes a resultant force making the cone move and since the current is alternating the direction of the force on the cone changes as the current changes direction, this causes the cone to move in and out resulting in a sound wave, if you increase the frequency of the A.C supply a higher pitch sound will be produced, and the opposite will happen if you decrease the frequency, if you increase the size of the current then the amplitude of the vibrations(increases volume)
explain how a moving coil microphone works
we have a flat sheet called the diaphragm, we also have a permanent magnet with one pole wrapped in wire and the over pole is surrounding the wire in a circular shape, when sound waves hit the diaphragm they cause it to vibrate, now the coil is moving in and out of a magnetic field, due to the generator effect a potential difference is created, since the wire is moving in and out of the magnetic field a changing potential difference is created, the frequency of the changing potential difference is the same as the frequency of the sound waves, the changing potential difference pattern is now passed through an amplifier and then into a moving coil loudspeaker, this massively increases the volume of the sound
explain how the generator effect works
as a wire is moved through a magnetic field perpendicularly a potential difference is induced and if the wire moves in the opposite direction a potential difference is induced in the opposite direction to the other potential difference, if the wire or magnet are not moving perpendicularly no potential difference is created, if a closed loop of wire (a circuit) is passed through a current is created and this current follows the same rule as the potential difference, you can increase the strength of the potential difference or current by increasing the strength of the magnetic field, moving the wire or circuit more rapidly, turning a wire/circuit into a coil all these things increase the strength, as the wire or circuit is passed through the magnetic field an opposing magnetic field is created this field counter acts the direction the wire or circuit is being pushed and if the direction the wire or circuit is being pushed changes the opposing force will also change, this opposing force happens because working is being done and energy is being transferred to the wire
what is newtons first law of motion
unless a resultant force is acting on an object it will remain stationary or in the same motion(inertia)
what is newtons second law of motion
resultant force = mass x acceleration, the acceleration of an object is proportional to the resultant force on the object and is inversely proportional to the mass of the object
what is newtons third law of motion
when ever two objects interact with each other, they exert equal and opposite forces on each other(these forces are all ways the same type of force)
what is inertial mass and what is the equation for it
inertial mass is the measurement for how hard it is to change the velocity of an object, the equation for it is Inertial mass = force/acceleration
what is a transformer and what is made out of
a device that can change the size of an alternating potential difference, a basic transformer consists of two coil of wire(the primary coil and secondary coil) wrapped around an iron core (iron is used because it is easily magnetised and demagnetised)
how do transformers work
an alternating current runs through the primary coil this creates an alternating magnetic field and because of the generator effect an alternating potential difference is created in the secondary coil
how do alternators work how do dynamos work
Alternator
A coil attached to a slip ring commutator this means that each end of the coil is always attached to one end of the circuit that the generated current goes to, the coil rotates in a magnetic field this generates a current(the coil always rotates in the same direction, but the each side of the coil changes the direction it moves every half turn), and in the generator effect when a wire moves in an opposite direction to the direction it moved before, an opposite current is generated, this leads to the coil of wire creating an alternate current
The current is increased in the magnification of the magnet increases or if the number of turns in the coil changes
A dynamo works with the same principles as an alternator except a split ring commutator is used this means that every half turn each end of the coil switches which ring it is connected to this makes the current direct
describe a longitudinal wave
The oscillations of the wave are parallel to the direction of the direction in which the waves transfer energy, a longitudinal wave made up of areas of compression and rarefaction
describe a transverse wave
The oscillations of the wave are perpendicular to the direction in which the waves transfer energy
why do we run a high voltage through power lines
it reduces power loss over long distances because less energy will be lost due to surroundings
