Is this even written in English?

Sometimes just trying to interpret the jargon in a physics textbook, can seem as monumental as deciphering the Rosetta stone. You know that once you cross the barrier of language, you can truly appreciate the meaning and beauty of the physics underneath it all, and all the pieces will come together. That’s why in this article I’ll walk you through some of the key words and phrases you’ll encounter in each of the modules and demystify the jargon, so you know exactly what you’re reading and exactly what it means!

Onto the definitions…

Space

Term Definition/Concept Explanation/Example
 Gravitational Field A gravitational field is a region of space around an object that results in an attractive force around it that drags objects to the centre The gravitational field around the Moon, is weaker than the field around the Earth, hence why you weigh less on the moon. Your mass is the same in both instances, the Moon’s pull is just weaker.
 Gravitational Force The attractive force between two bodies, that results from the interaction of their gravitational fields The Earth and moon both have significant gravitational fields around them, the interaction between their fields results in an attractive force between them given by Newton’s law of gravitation: F = Gmm1/r^2
 Work Work is done on an object when a force causes the object to move When you lift a ball, and drop it. Gravity is doing work on the ball, to move it towards the ground. We’ll explore this further in the next definition.
 Gravitational Potential Energy The work done to move an object from a very large distance away to a point in a gravitational field What’s the deal with a ‘large distance away’. Fields never end, they go on to infinity – they just get weaker and weaker. This is why we say ‘a very large distance away’. If you’re on Andromeda the Earth’s gravitational pull is negligible.
 Projectile An object that moves only under the influence of gravity If you throw a stone the only force affecting it is gravity (ignoring air resistance), so it is a projectile. A rocket is not a projectile, since, in addition to gravity, we also have thrust from the engine in play.
 Escape Velocity The minimum velocity required for an object to escape from a body’s gravitational field If I had a tennis ball and a racket, and I hit the ball into the sky. How fast would I have to hit it, so it never came back to Earth? That’s the escape velocity. As you can imagine it would have to be pretty fast, around 11.2 kilometres a second to be precise!
 G-Force The ratio of the normal force to the weight force In an elevator accelerating up at g, your weight is mg, but the normal force is 2mg due to the addition of the elevators acceleration. Thus the ratio of the normal force to the weight force is 2:1 more commonly referred to as 2g.
 Aether A proposed substance that permeated all matter, and which light would travel through Sound needs a medium to travel – space is a vacuum so we can’t hear sound. Water waves need water. What about light, surely that needs a medium? Let’s call it the aether. (We’re now pretty sure light doesn’t need a medium. This is just what scientists thought at the time. See below)
 Michelson-Morley Experiment An experiment designed to test the velocity of light passing through the aether. When you’re standing outside you don’t really feel the air, but if you stick your hand out a car window you feel the wind. A similar effect should happen if the Earth is moving through an Aether, we should be able to feel a wind. Michelson and Morley tested if there was a wind, they didn’t detect one.
 Frame of reference A point of view from which an observer can make measurements From the Earth’s frame of reference, the moon appears to orbit the earth. From the moon’s frame of reference, the Earth orbits the moon.
Inertial frame of reference An inertial frame of reference, is a frame moving at a constant velocity. Sitting in a train moving at a constant speed.
Non-inertial frame of reference A non-inertial frame is one that is accelerating. Sitting in a car taking a turn.
 Time Dilation The phenomenon that moving clocks run slower to a stationary observer. If I’m moving you see my watch tick slower.
 Length Contraction The phenomenon that moving lengths appear shorter to a stationary observer. If I’m holding a metre ruler and running, as far as you’re concerned it’s no longer 1 metre, its shrunk!
 Mass Dilation The phenomenon that moving object are heavier when measured by a stationary observer. If a rocket is moving, it gets slightly heavier from your perspective
 ‘Relativity of Simultaneity’ Two events that appear to happen at the same time in one inertial frame, may not in another. If you see two doors close at the same time, and I’m running past you, from my perspective the doors don’t seem to close at the same time.

Motors and Generators

Term Definition/Concept Explanation/Example
Current  The flow of electric charge  A common misconception is that current is defined as the flow of electrons. Conventional current is NOT always the opposite of electron flow, it just happens to be in a metal wire, which is the majority of what is studied in HSC physics hence the cause for confusion. There are instances where this is not the case though, e.g. in semiconductors, or some ion batteries for you HSC Chemists.
Torque  A measure of the ability of a force to cause rotation. T=Fd  Have you ever changed a car wheel or seen someone do it? You’ll probably notice a very large wrench is used. Why don’t we use a portable wrench that fits in a pocket? Larger wrenches produce more torque making bolts easier to loosen since torque is proportional to distance.
Motor Effect  The phenomenon that current carrying conductors experience a force in a magnetic field. F= BIlsinθ This is the reason a motor spins. When current is passed through the coils in the magnetic field, due to the motor effect they begin to spin.
Galvanometer  A device used to measure current.  The force that turns the coil in the galvanometer is proportional to the current, we can use this fact to make a scale that measures current.
Loudspeaker  A device capable of producing sound.  A current is passed through a coil, connected to a diagram. The coil moves when a current is passed through it due to the motor effect. This movement causes the diaphragm to vibrate air particles producing sound.
DC motor A device capable of turning DC electrical energy to mechanical energy.  A DC current is passed through a coil, causing it to rotate due to the motor effect. This is how your PlayStation or Xbox controller rumbles, there’s a tiny DC motor inside it, with an unbalanced weight causing the controller to shake.
Faraday’s Law of Induction The phenomenon that a conductor exposed to a changing magnetic field produces an EMF.  Moving a magnet near a conductor exposes the conductor to a changing magnetic field. A small current would be produced in the wire by Faraday’s law which you could measure with the galvanometer.
Lenz’s Law The direction of the current induced by a changing magnetic field is such that it produces a magnetic field which opposes the original change that created it.

 What a mouthful, this is just a fancy way of saying the universe doesn’t like change. If a conductor is initially exposed to 0 magnetic fields, and you start moving a magnet above it. The universe is like stop that, and the conductor produces a magnetic field which cancels out yours.
Supply EMF  The voltage source to a motor, causing it to spin.  This is usually a battery.
Back EMF  The voltage induced in the motor due to the motor spinning.  Because the coils in the motor are moving in a magnetic field. They experience a change and by Faraday’s Law an EMF is induced. Lenz’s law tell us the direction of the current will be such that it opposes the rotation, that is directly opposite to the supply EMF hence the name Back EMF.
Eddy Current  A circular flow of current induced in a conductor due to a changing magnetic field.  If you move a magnet above a copper plate, an EMF is induced. The electrons want to move but there’s no real path to follow this is just a sheet, not a wire, so they just form a conga line and move in a circle.
Generator  A device which turns mechanical energy into electrical energy. The snowy mountains scheme actually employs generators to provide power. Water falls from a dam, spinning a turbine. This causes coils to spin in a magnetic field, which by Faraday’s law induces an EMF in the coil.
Transformer  A device which can change AC voltages.  Transformers are referred to as ‘step up’ when they take in a supply voltage and increase it. They are referred to as step down when they take in a supply voltage and decrease it.

Ideas to Implementations

Term Definition/Concept Explanation/Example
Cathode Ray A stream of light, observed inside an evacuated tube subjected to a high voltage. We now know the cathode ray is a stream of charged particles, specifically electrons. Physicists did not know this until J.J Thompsons great charge/mass ratio. Cathode rays were used in old CRT (Cathode Ray Tube) TV’s to produce pictures.
Electron Gun  A device used to eject electrons  It consists of two electrodes referred to as the cathode (negative) and anode (positive), between which there is a large potential difference causing electrons to be ejected from the cathode towards the anode. There is also usually a heated filament, which assists with electron ejection due to thermionic emission.
Deflection Plates Two electric plates used to manipulate the movement of cathode rays. Depending on the polarity of the plates we can control the movement of the electrons. They are always attracted to the positive plate, if we have the positive plate at the top, the electrons move to the top and vice versa.
Helmholtz Coils  A set of conducting coils producing a magnetic field used to manipulate the movement of cathode rays.  When a steady current is passed through a wire, a magnetic field is produced as first observed by Ørsted. If we have two circular coils we can produce a strong magnetic field between them. When electrons pass through this field they will change direction.
Oscilloscope  A device which displays a changing voltage as a graph on a screen.  If there is a problem with a circuit, an electrician can connect an oscilloscope to a circuit, and visually see any changes in the voltage pattern to diagnose problems with the circuit.
Photoelectric Effect  The phenomenon where electrons are ejected from a metal surface after being struck by EMR above a certain frequency This is how some automatic doors work at the supermarket. When you walk towards the door, you block some light from the detector, in doing so you change the amount of electrons flowing in the circuit when this change is measured the door opens.
Semiconductor  A substance with conductivity lower than a conductor but higher than a \, which carries charge via holes or free electrons. Usually from group IV  This rough definition is the best we can do for the HSC level, a full explanation requires theory beyond the scope of the HSC. The qualitative understanding of their level of conductivity is sufficient.
Doping  The addition of a few foreign atoms to a semiconductor lattice to alter its electrical properties.  This name is suggestive of what we’re trying to achieve. In much the same way Doping is a cloud over sport, as it can enhance the athletic performance of the athlete. We often dope semiconductors in an effort to boost their electrical conductivity.
P-type semiconductor  A semiconductor doped with an element from Group III, increasing its conductivity.  Group III elements have three valence electrons, and so when covalently bonded with silicon which has 4 valence electron, one of the bonds is incomplete leaving a hole. Electrons are free to move into this hole, when they do move they create a new hole where they moved from. The hole facilitates the movement of electrons and thus it increases the conductivity of the semiconductor.
N-type semiconductor  A semiconductor doped with an element from Group V, increasing its conductivity.  Group V elements have five valence electrons, and so when covalently bonded with silicon which has 4 valence electron, one electron is left over. This electron is free to move and thus it increases the conductivity of the semiconductor.
Thermionic Diode/Solid state Diode  A device used to produce unidirectional current.  A diode ensures current passing though it always goes in one direction. Current in the wrong direction will be unable to pass through.
Thermionic Triode valve/Solid state transistor  A device which can act as a switch or an amplifier  These devices are a fundamental part of the computer revolution. They are used for digital logic. The more you can fit, the smarter your computer is. Your smart phone has around 2 billion transistors in it!
Superconductor  a substance which exhibits 0 resistance when below a certain temperature known as the critical temperature The superconductor with the highest critical temperature as of publishing this article is Mercury Barium Calcium Copper Oxide which has 0 resistance at around -140 degrees celsius. Finding superconductors with a critical temperature closer to room temperature is an important area of research. It would revolutionise the modern world.
Meissner Effect  The phenomenon that a superconductor excludes all external magnetic fields.  This is why superconductors hover. If you place the superconductor above a magnet, the field attempts to penetrate the superconductors, but due to the Meissner effect, the superconductor excludes the external field and rises.

 

Practice Makes Perfect

The best way to know what these definitions all really mean is to read them and apply them within context. To help you out with that, we’ve compiled a master list of practice papers (with ANSWERS!!!) to help you get prepared

Good Luck!

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Vamsi Srinivasan is looking to uncover the next hidden truth of the universe. He was so fascinated by the beauty of Physics and Mathematics during his HSC that he went on to study Physics at University. He is now in his second year of a dual degree in Physics/Computer Science. He loves physics and maths so much, he wanted to share his passion and has been an Art of Smart coach for the past 2 years. He’s helped coach students in physics as well as all ranges of HSC Maths from General to Extension 2. In his spare time you can find him watching Tennis or Formula 1 or perhaps listening to his favourite podcast ‘Hello Internet’.