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Recap on All Summer Work(Physics) 1 - Coggle Diagram
Recap on All Summer Work(Physics) 1
Superposition
Superposition is the ability for waves to interfere and "combine", causing constructive or destructive interference.
When two waves are identical and of the same period, perfect constructive interference will be observed.
When two identical waves are half a wavelength apart (one wave reaches maximum amplitude when other reaches minimum amplitude), perfect destructive interference will take place.
Fourier's Theorem states that "any continuous wave can be produced through the superposition of sinusoidal or cosine waves.
A spectrum analyser can break down a superimposed waves into its constituent parts similarly to the way in which a Newtonian prism can break down light into its constituent wavelengths.
Path and Phase Difference
The "distance" between two nodes is always half a wavelength.
Path difference(Δx) is the distance that two waves from different sources have to travel before intersecting/interfering.
If there is no path difference or the path difference is an integer multiple of the wavelength, constructive interference will take place.
Waves are coherent if they are produced by different wave sources and are of a constant phase difference. These waves will have the same wavelength.
Phase difference(ϕ) is measured in radians/degrees.
If there is a path difference (of coherent waves) of an integer multiple of half a wavelength, destructive interference will be observed.
Harmonics and Standing Waves
Unlike progressive waves (that transfer energy), standing waves store energy.
The first standing wave that we can produce is known as the fundamental; its 2 nodes are located at its two fixed points (no "internal" nodes) and it has a length of 1/2 lambda. Therefore the wavelength is equal to the 2L where L is the length of the string.
n/2 = L
(where n is the harmonic number = number of antinodes)
f = 1/2(L ⋅ sqrt( T / μ )
(where T is the string's tension and μ is the mass/unit length.
Impulse and Momentum
Impulse is defined as the force applied to an object with respect to a change in time, therefore:
Impulse = Force ⋅ Change in Time
Integrating a function of force with respect to time would give us the impulse.
Types of Collisions
Within an elastic collision, the co-efficient of restitution = 1. No kinetic energy is lost within these collisions and the objects separate afterwards.
Within an inelastic collision, the co-efficient of restitution < 1. The objects will separate but kinetic energy will be lost.
Within a perfectly inelastic collision, the co-efficient of restitution = 0. The objects stick together after the collision and some kinetic energy goes into such mediums as sound, heat,
etc
.
The co-efficient of restitution(e) is defines as the ratio of the velocity of an object before a collision to the velocity of an object afterwards.
Magnetic Fields
The Earth's magnetic field is generated through the movement of molten iron within its core (through convection currents generated by tremendous heat and pressure).
Within a magnetic field diagram, the direction of field lines travels from north to south, the closer these field lines are, the stronger the magnetic field strength.
A compass contains a bar magnet, the needle of this compass points in the direction of the Earth's magnetic field.
Electromagnets
When a current flows through a wire, it produces a magnetic field around the wire, the direction of the field lines of this field can be found using the right hand rule.
The strength of an induced magnetic field(Tesla) is dependant on the size of the current.
Solenoids are coils of wire with a current passing through (magnetic fields generated through induction). These types of magnets can simply be turned on and off.
The larger the number of coils in a solenoid, the greater the magnetic field.
The Motor Effect
When a wire carrying an electrical current passes through a magnetic field perpendicular to the field lines, a force is exerted on the wire; we can use Fleming's left hand rule to find the direction of this force.
F = BIL
Speakers work through the movement of a cone as a result of a changing magnetic field. This alternating magnetic field is generated using an alternating current through an electromagnet. The movement of this cone generates sound waves with a frequency equal to that of the alternating current.
Generators
Whilst a motor converts electrical energy to kinetic energy, a generator converts kinetic energy to electrical energy.
When a conductor experiences a change in magnetic field, a potential difference is induced on the conductor. If this is part of a complete circuit, a current will flow.
Electricity can be generated faster through: more coils on a solenoid, stronger magnets and a "faster spin".
Electromotive force is defined as the energy converted from an energy source (such as a battery or a generator) to electrical energy per unit charge.
An alternator generator produces an alternating current, the coil within these generators are connected to two separate commutators. The alternating current increases if the magnetic field strength increases and/or the number of coils is increased. If we increase the rotation speed of the coil, the alternating current and its frequency increases.
A dynamo generator generates a direct current through the use of s split ring commutator. When graphing the potential difference against time for these generators, the function y = |sin(x)| will be seen.
Transformers
A step up transformer will have more coils on the secondary coil than the primary, the inverse is true for a step down transformer.
1) An alternating p.d is applied across the primary coil, creating an alternating current to flow and henceforth an alternating magnetic field around the coil.
2) Because the iron core is magnetic, the alternating magnetic field around the coil induces an alternating magnetic field on the iron core.
3) This induces a potential difference on the secondary coil, causing a current to flow through it.
The transformer process transfers a current from one coil to another through induced magnetic fields rather than wires directly; this would not be possible as the wires are insulated.
Lasers and Stimulated Emission
Laser - Light Amplification by Stimulated Emission of Radiation.
Stimulated emission is a process where an excited electron is forced into a de-excited state by the E and M fields of an EM wave. The energy of this photon must be the same as the electron's "drop energy".
Stimulated emission results in one further electron being emitted as a result of the de-excitation
During excitation, if an incoming photon has enough energy, it can liberate an electron from its atom completely (ionisation). This process can better be explained by the particle model of light.
E = hf
Energy of single photon = Frequency x Planck's Constant