Definitions!

[myanacondadont]

So, like most people I often struggle to find the correct words in my worded responses to get full marks so I was wondering if someone could look over the definitions I'm going to write on my cheat sheet. Thanks - I can't remember if I've forgotten any important ones but if I have tell me ! Also they are prob a bit long for actual answers on the exam, so I can edit/remove parts to perfect it to the queston.

Apparent weightlessness:
Apparent weight is given by the normal force. When falling at the same rate of gravity (i.e freefall) the net force is entirely given by the force of gravity, hence force of the normal is equal to zero therefore apparent weightlessness occurs. However a gravitational field strength still exists and you still have weight (as W=mg).

Modulation:
A variation in the initial signal is converted to a variation in the end signal (e.g amplitude, brightness etc).

Iron core in transformers:
Used to strengthen the magnetic field. The iron core acts as an induced magnetic itself and creates a magnetic field in the same direction as the external, strengthening it.

Clipping:
A form of distortion, occurring when the input signal is outside the amplifiers input limits (can be potentially rectified by biasing the transformer - placing it in the middle of all possible output values to avoid clipping). Not sure what else to add - I remember reading an assessor's report a while ago that condemned students for giving a 'generic' response of clipping....How do you avoid that?

Standing Waves (demonstrates electrons exhibit wave-like properties - De Broglie wavelength etc):
A standing wave is formed when the circumference of the orbit of an electron is reinforced by a WHOLE number of De Broglie wavelengths of the electron. Only electrons with energies related to those particular wavelengths will form stable levels hence their quantized nature.

Operation of Transformers (kinda sketchy on this one):
Transformers operate on the principle of electromagnetic induction. An AC voltage will create a change in flux in the primary coil which in turn (Due to Faraday's law) creates a change in flux in the secondary coil. Therefore the secondary coil will attempt to oppose the change in flux, inducing a voltage. DC Voltage does not alternate and therefore does not create a change in flux - hence it does not work in cooperation with transformers.

Commutator's:
A Commutator switches the terminals of the power source every half turn. This in turn reverses the direction of the current every half turn, allowing the coil to rotate in a constant direction (due to a constant rotational force (is torque incorrect to say here? I remember an assessor's report that said torque is incorrect))

Random stuff - not necessarily definitions but rather observations;

Young's double slit experiment:
Demonstrated light can produce interference patterns (a wave-like characteristic). The interference pattern is produced by constructive/destructive interference producing the antinodal points (bright fringes) due to constructive and nodal points (dark fringes) due to destructive interference. The particle model predicted 2 bands of light behind the slits - this was not the case, hence it supported the wave model of light.

Photoelectric effect:
Demonstrated light has a few characteristics that are failed to be explained by the wave model, supporting the particle model.
Kinetic energy is independent of brightness/intensity. Rather that an increase in intensity just increases the number of photoelectrons emitted. Particle model could explain this yet the wave model predicted an increase in intensity would increase the kinetic energy.
Kinetic energy is proportional on frequency (What else do I say, how do I explain that wave model failed to explain this?)
Cut-off frequency.
No time delay in the emission of photoelectrons.

Compton effect(supports particle model):
Photon's have momentum even though they are mass-less.

So if anyone can have a look over and see if I've got some fundamental understanding wrong that'd be great (particularly transformers). Feel free to post some definitions of your own!

[Avainer]

You need split ring and slip ring commutator definitions too! I'll dig up the sheet of definitions a lecturer gave me (Colin Hop) and get you some of the sketchy ones if I ever find it.

[Zealous]

is torque incorrect to say here?

I probably wouldn't discuss torque for this. A definition similar to one given on each examiner report probably covers enough points.

I think maybe torque was incorrect to say if people thought there was torque when a coil is in a vertical position - but there would be no component of the forces on the coil to generate any torque. In fact, using a split ring commutator, there aren't any forces acting on the coil when it is in its vertical position (as the commutator disconnects current briefly before switching) and it's a bit of momentum which continues the rotation before the current kicks in again.

Kinetic energy is proportional on frequency (What else do I say, how do I explain that wave model failed to explain this?)

The wave model describes transfers as a continuous transfer of energy (as opposed to the one to one nature of the photon model), and the intensity of light is based on a wave's amplitude. Basically with the wave model, you would expect the energy of light to increase with the intensity (amplitude) but this is not observed with the photoelectric effect - instead changing the intensity of light simply affects the photocurrent which is best explained by the photon model (more intensity = more photons).

I remember reading an assessor's report a while ago that condemned students for giving a 'generic' response of clipping....How do you avoid that?

You can probably make it less generic by using information from the question - so mention the range where the input voltage would be cutoff, and describe what the flattened out voltage would be like (what the cutoff output voltage is).

Hopefully I haven't made any theory mistakes, it's not my strongest point.

[Daniel Target]

Hey could someone please share their explanation of wavelike nature of electrons and why they support discrete energy levels and standing waves etc?

[myanacondadont]

Hey could someone please share their explanation of wavelike nature of electrons and why they support discrete energy levels and standing waves etc?

I can try.
Electrons have a wavelength (De Broglie). As such, they exhibit wave-like properties and can form standing waves. A standing wave is formed when the circumference of the orbit of the electron is reinforced by a whole number of wavelengths. Only electrons with energies related to those particular wavelengths will form stable levels hence their quantized (discrete) nature.