AS Unit 1 Physics Flashcard Deck

Pregunta	Respuesta
How to calculate specific charge?	Charge / Mass i.e. Charge-Mass ratio
What is an isotope?	A variant of an atom that has an equal number of protons but a different number of neutrons to the original.
What are the forces acting on the nucleons in a nucleus called?	Electromagnetic - repel Gravitational - attract Strong Nuclear Force - attract
What is the general equation for alpha decay?	Image: Alpha_Decay.gif (image/gif)
What is the general equation for beta-minus decay?	Image: Beta-Minus_Decay.gif (image/gif)
What happens in pair production?	A photon of sufficient energy splits into a particle-antiparticle pair.
What happens in annihilation?	A particle and antiparticle collide and annihilate each other. All the mass of the two particles are converted into energy in the form of two gamma photons.
Name two baryons	Proton Neutron
Name two mesons	Pion Kaon
Name two leptons	Electron Muon
What is the quark composition of a baryon?	Three quarks
What is the quark composition of a meson?	Quark-antiquark pair
Why do leptons not have any quarks?	Because leptons are fundamental particles - just like quarks.
What is the photoelectric effect?	In the photoelectric effect, electrons are emitted from solids, liquids or gases when they absorb energy from light of high enough frequency. Electrons emitted in this manner may be called photoelectrons.
Diagram of the photoelectric effect?	Image: The_Photoelectric_Effect (image/jpg)
How do you calculate threshold frequency?	f = Φ / h
How do you calculate photon energy?	Φ = hf - EKmax
How do you convert electron volts (eV) to joules (J)?	1 eV = 1.6 x 10^-19 So multiply by 1.6 x 10^-19
What makes an atom excited?	When one or more of its electrons is in an energy level higher than the ground state. Electrons can move down an energy level by emitting a photon of equal change in energy.
What makes an atom ionised?	When an electron has been removed entirely from the atom. The ionisation energy is the energy needed to remove an electron from the ground state atom.
What do line spectra provide evidence for?	That electrons can only exist in discrete energy levels. Atoms can only emit photons with energies equal to the difference between the two energy levels. Since only certain energy levels are allowed, the corresponding wavelengths can be seen in the line spectrum.
What are line absorption spectra?	You get line absorption spectrum when light with a continuous spectrum of energy (white light) passes through a cool gas. Photons of the correct wavelength are absorbed by the electrons to excite them to higher energy levels. These wavelengths are then missing from the continuous spectrum when it comes out of the other side of the gas.
Is light a wave or a particle?	Neither - light exhibits wave-particle duality.
Where does light exhibit wave and particle properties?	Diffraction of light as they pass through a narrow slit shows light as a wave. Particles would either not go through the gap due to being too large or just pass straight through, leaving the beam unchanged. The photoelectric effect shows light as particle-like photons. If a photon of light is a discrete bundle of energy, then it can interact with an electron in a one-to-one way. All the energy in the photon is given to one electron.
Do electrons have wave-particle duality?	Yes - electron diffraction can prove this. Diffraction patterns are observed when accelerated electrons in a vacuum tube interact with the spaces in a graphite crystal sheet. As they pass through the spaces, they diffract just like waves passing through a narrow slit and produce a pattern of rings.
What is current?	Current is the rate of flow of charge, measured in amperes (A).
What is potential difference?	The work done in moving a unit charge between two points, measured in volts (V).
What is resistance?	A measure of how difficult it is to get a current to flow through a component, measured in ohms (Ω).
What makes a conductor an ohmic conductor?	When current is directly proportional to potential difference (Ohm's law). This forms a straight line of a constant gradient on an I-V graph.
Are metallic conductors ohmic?	Yes - provided they are kept at a constant temperature. Their characteristic I-V graph is a straight line as their resistance doesn't change.
Are filament lamps ohmic?	No - their characteristic I-V graph is a curve that starts steep but gets shallower as the voltage rises. This is due to an increase in temperature as a result of an increase in current. This rise in temperature causes a higher resistance due to more 'vibrations' in the electrons, making it harder for charge to flow. Eventually, the current and temperature cancel each other out, meaning current levels off at high values.
Give examples of semiconductors.	Thermistors Diodes Light Dependant Resistors
What is resistivity?	A measure of how much a particular material resists current flow,measured in ohm metres (Ωm). It depends on the structure of the material as well as environmental factors such a temperature and light intensity.
What are superconductors?	You can lower the resistance of many materials by cooling them down. If you cool some materials below a transition temperature, they become superconducting - zero resistance. This is usually around 10 kelvin (-263 degrees Celsius), thus it is very difficult and expensive to achieve. Superconductors have uses as long range power cables that do not lose power, really strong electromagnets in maglev trains, or in PCBs that work really fast.
What is power?	The rate of transfer of energy, measured in watts (W).
How do you calculate the total energy transferred in a given time?	E = VIt E = (V^2 / R)t E = I^2Rt
What is internal resistance?	The resistance due to the power source itself, measured in ohms (Ω).
What is e.m.f.?	The amount of electrical energy the battery produces and transfers to each coulomb of charge, measured in volts (V).
How do you calculate electromotive force?	ℰ = I(R + r)
How can you use a V-I graph to find values for internal resistance and e.m.f.?	Y-intercept c = ℰ Gradient m = -r
Summarise Kirchhoff's laws.	I(in) = I(out) ℰ = ΣIR R(total) = R1 + R2 + R3 1 / R(total) = 1 / R1 + 1 / R2 + 1 / R3
What is a potential divider?	Potential dividers divide up the voltage within a circuit, so that parts of a circuit only receive the voltage they require. Potential dividers usually consist of two or more resistors arranged in series across a power supply.
What is an alternating current?	A current that changes with time i.e. a sin wave.

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AS Unit 1 Physics Flashcard Deck

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