Mixed Prompt Questions Flashcards
What’s the difference between potential difference (p.d.) and electromotive force (e.m.f.)?
p. d. is the electrical energy transferred between two points.
e. m.f. is the energy supplied to a circuit.
Explain the shape of a current-voltage graph for a filament lamp (curved and levels off).
V is proportional to I up to point (x).
Begins to curve because as I increases, T increases.
When T increases, R decreases.
Explain the shape of a resistance-temperature graph in terms of the structure of a metal (straight line, not through the origin).
As T increases, particles in lattice structure vibrate more because KE increases.
As KE increases, electrons collide more frequently with lattice.
More E is dissipated, so for constant I, V must increase.
R=V/I therefore as T increases, R increases.
Explain the atomic process that produces emission spectra.
Electron jumps down.
Energy levels.
One photon released for every electron.
E=hf.
Will a fixed target or colliding beams create a new particle with the largest mass?
Fixed target:
Momentum before, so momentum after.
Particles create some KE.
Not all KE turned into mass.
Colliding beams:
Total momentum before is zero, so total momentum after is zero.
If one stationary particle created all KE turns into mass.
Therefore colliding beams create a particle with the largest mass.
Describe what happens in a bubble chamber.
Tracks indicate charged particle.
Gaps indicate neutral particles.
Tracks in different directions indicate momentum is conserved.
Particles collide with stationary particles.
Define ductile.
Can be dawn out into wires.
Undergoes large plastic deformation.
Define brittle.
Shatters when subject to impact.
Define strength.
Stress needed to break.
Define hardness.
Resistance to indentation.
What are the discussion points around a stress-strain graph?
high stress = higher strength
high elastc limit = return to original shape.
large area under graph = absorbs energy.
steep grad. = less strain for stress.
Why are ‘these’ electrons useful for investigating nuclear structure (in a particle accelerator)?
Wavelengths need to be smaller than nuclei.
How does helium in the sun’s atmosphere cause a set of dark lines?
A photon absorbed by an electron.
Electron moves to a higher energy level.
Where photon energy = difference in energy levels.
Only certain changes/differences possible.
Between discrete energy levels.
Why do energy levels have negative values?
Just-free electrons have zero energy state.
Electrons need to gain energy to move to a higher level.
What is the de Broglie wavelength?
The wavelength associated with a particle/electron.
With a given momentum.
Why does a stick look broken in water?
There is a change in density from water to air.
This causes a change in direction of light (away from normal travelling from
water to air).
So light appears to come from a different point of origin.
Define refraction.
Change in direction of wave.
Due to change in density.
Define total internal reflection.
Angle of incidence greater than the critical
angle.
When light within a denser medium strikes a boundary with a less dense
medium.
All of the light is reflected.
How do magnetic fields curve particle paths?
Magnetic field is perpendicular to the motion of particles.
Magnetic force and acceleration act towards the centre.
F = Bqv = mv^2/r
r is constant.
Explain why only certain wavelengths of light are emitted.
Electrons/atoms move to higher energy levels
Or Electrons/atoms are excited
They then move to lower energy levels (accept ground state)
The energy (from the change) is given out in the form of a photon
The energy levels are discrete Or only certain energy levels are possible
The energy of the photon must be equal to the difference in energy levels
Or hf=E2 −E1 Or hc/λ=E2 −E1
There are only a limited number of energy differences and only a corresponding
set of frequencies/wavelengths (looking for energy differences /changes not
energy levels)
Explain what happens to the capacitor as it becomes fully charged.
The idea that electrons move from one plate to the other plate through the external circuit.
When fully charged there is no movement of electrons.
Describe what happens to the current through the resistor as a capacitor discharges.
Current decreases (over time).
Exponentially.
What is binding energy?
The energy equivalent to the mass deficit
When nucleons bind together to form an atomic nucleus
