CAP 3 Flashcards
Why is it important to test by experiment the prediction of a scientific theory?
if a reliable experiment supports a theory, the theory can be accepted, and extended on
if a reliable experiment does not support a theory, the theory must be changed
What is the strong nuclear force?
The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
What is meant by the emf of a battery? (Explain in two ways)
emf is the chemical energy transferred into electrical energy in the battery per unit charge passing through
or the pd across terminals when no current is passing through the battery
Suggest how two lamps can have different power rating but have the same intensity output
in lamps energy is wasted as heat (thermal energy)
one lamp may waste more energy than the other, as in less energy is converted into light
State what is meant by the centre of mass.
the centre of mass is the point through which the line of action of a force has no turning effect
it is where the mass of the body can be considered to be concentrated
State what is meant by superconductivity.
Explain the required conditions for the material to become superconducting
superconductivity means a material has zero resistivity, and zero resistance at or below a critical temperature
resistivity decreases with temperature
so the material becomes superconducting when you reach the critical temperature
State the role of exchange particles in the creation of forces between particles
The force arises when the exchange particle moves between the other particles
State the names of the particles that are produced when a muon decays.
Electron + an electron antineutrino + muon neutrino
State on application of a polarising filter and give a reason for its use
Polaroid sunglasses - to reduce glare
Name a way to detect if an electron has been released from an experiment
Using a cloud chamber
Give two properties of hadrons that distinguish them from leptons.
hadrons experience the strong interaction, leptons don’t
hadrons are made up of quark, so are not fundamental, leptons are fundamental
For a sound wave, explain what is meant by wavelength
wavelength is shortest distance between two points in phase
it is the distance between two adjacent compressions (or rarefactions)
Explain, in terms of electron motion, why the I–V characteristic for the filament lamp is a curve.
An increase in current/voltage leads to an increase in temperature, as electrical energy is converted into heat energy
So the metal ions vibrate with increased amplitude
And therefore an increase in the rate of collisions of the lattice ions with electrons
This impedes the movement of electrons through the lamp
So the resistance increases as shown by V being not proportional to I on the graph
Explain why the unloading line on a force/extension graph of a material that has been plastically deformed is parallel to the loading line, but doesn’t run through the origin
Plastic deformation has produced permanent extension
There has been re-alignment of bonds in materials hence the intercept is non-zero
But the gradient is the same because after extension the force between bonds is identical to before (ie the stiffness constant hasn’t changed)
Explain why it is necessary for many teams of scientists and engineers to collaborate in order for advances to be made in particle physics.
results of experiments must be independently peer reviewed before they are accepted ✔
particle accelerators are very expensive and collaboration helps to spread the cost of building them ✔
many skills and disciplines are required (which one team are unlikely to have) ✔
lots of data to process (so more teams needed) ✔
Explain what is meant by the internal resistance of the battery.
the resistance of the materials within the battery
It is the hindrance to flow of charge in battery
Explain what is meant by a progressive wave
A wave transfers energy from one point to another ✔
without transferring material ✔
Explain how the resistance of a lamp varies as the voltage across it is increased from zero to its working voltage
As voltage increases, temperature increases. The lattice ions are vibrating with increased amplitude, so there is an increased frequency of collisions of eletrons with the lattice ions, therefore resistance increases.
Explain how a bright line is formed by the diffraction grating at the first-order diffraction angle
light from each slit superpose
light from adjacent slits have a path difference of one wavelength
at this angle all the waves are in phase
constructive interference occurs
During the photoelectric effect, explain why, when ultraviolet light is shone on a positively charged plate, no charge is lost by the plate.
The process involves the ejection of electrons which are negatively charged
Any electrons ejected will only make the positive charge greater
Describe what is likely to happen to a positron shortly after its creation.
It will meet an electron, and annihilate. It’s mass will be converted into two or more photons travelling in opposite directions in order to conserve momentum
What is potential difference?
Potential difference is the work done moving a unit charge between 2 points in a circuit
What is resistance?
Resistance is how difficult it is for current to flow through an appliance
R = V / I
What is Ohm’s law?
Current is directly proportional to potential difference providing physical conditions remain constant
