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148 Cards in this Set
- Front
- Back
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Displacement |
The distance from a fixed point along a particular direction |
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Velocity |
The rate of change of displacement (m/s) |
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Acceleration |
The rate of change of velocity (m/s2) |
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Scalar quantity |
A quantity that has no direction eg mass |
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Vector quantity |
A quantity that has direction and magnitude associated with it (eg velocity) |
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Force |
Something that can cause acceleration (N) |
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Friction |
A force that opposes the movement of one surface over another |
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Momentum |
Mass × velocity (kgm/s) |
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Conservation of momentum |
In any interaction with no external forces the total momentum before is equal to the total momentum after |
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Newton's first Law of motion |
An object remains in a state of rest or in uniform motion in a straight line unless an external force acts on it |
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Newton's second law of motion |
The resultant force on an object is proportional to its rate of change of momentum |
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Newton's third law of motion |
If A exerts a force on B then B exerts an equal and opposite force on A |
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Weight |
The weight of a body is the force of gravity acting on it |
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Newton's universal law of gravitation |
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Density |
The mass per unit area (kg/m3) |
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Pressure |
The force per unit area (Pa) |
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Archimedes' Principle |
When a body is partially or wholly immersed in a fluid the upthrust is equal in magnitude to the weight of the fluid displaced |
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Law of floatation |
The weight of floating body is equal to the weight of fluid displaced |
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Moment |
Perpendicular distance × force |
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Couple |
A system of forces which have a turning effect only and the resultant is zero |
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Equilibrium |
When a body's acceleration is zero |
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Law of Equilibrium 1 |
The sum of the forces acting on the body is zero |
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Law of Equilibrium 2 |
The net total clockwise moment equals the net total clockwise moment |
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Energy |
The ability to do work |
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Principle of Conservation of energy |
Energy can neither be created nor destroyed merely converted from one form to another |
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Work |
Force × distance moved |
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Power |
Work done per second |
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Watt |
One joule per second |
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Efficiency |
Power in÷power out |
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Heat |
The measure of energy (Joules) |
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Temperature |
A measure of the hotness of a body (Kelvin) |
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Specific Heat Capacity |
The amount of energy needed to change the temperature of 1kg of that substance by 1 Kelvin |
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Specific Latent Heat |
The heat energy needed to change the state of 1kg of a substance with no change in temperature |
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Thermometric property |
A physical property that changes measurably with changing temperature |
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Conduction |
The transfer of energy through a substance without the movement of the particles of the substance |
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Convection |
The transfer of energy through a substance by the movement of the particles |
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Radiation |
The movement of energy in straight lines from the surface of a hot body without the need for a medium to pass through |
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Solar constant |
Amount of solar energy per second per 1m2 of area (Watts per m2) |
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U-value |
The u-value of a building material is the amount of heat energy that will escape per second through 1m2 of the material for each 1K temperature difference across it |
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Celsius |
Kelvin temperature - 273.15 |
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Boyle's Law |
When a fixed mass of gas is kept at a constant temperature its pressure is inversely proportional to its volume |
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Stationary wave |
A wave with no net transfer of energy formed by interference of two waves of equal frequencies and amplitudes moving in opposite directions |
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Harmonics |
Frequencies which are whole number multiples of a fundamental frequency |
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Resonance |
Transfer of energy between bodies with similar natural frequency |
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Sound intensity |
Sound energy per second crossing each square metre of area (Watts per m2) |
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Threshold of hearing |
The smallest intensity that can be heard by a human ear (1x10-12 W per m2) |
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Threshold of pain |
Intensities above 1W/m2 cause pain and permanent damage |
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Sound intensity level |
The change in sound intensity level is 1 Bel when the second sound intestinal is 10 times the first |
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dB(A) scale |
dB except has been adapted to take into account of how the human ear responds differently to different frequencies |
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The Doppler Effect |
The apparent change in frequency of a wave due to the relative motion between the source of the wave and the observer |
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The first Law of reflection |
The angle of incidence is equal to the angle of refraction |
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The second law of reflection |
The incident ray, the normal and the reflected ray are all in the same plane |
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The first Law of refraction |
Sin i/sin r = the refractive index a constant |
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The second law of refraction |
The incident ray the normal and the refracted ray all lie in the same plane |
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Power of a lens |
1/focal length in m |
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Critical angle |
The angle of incidence in the denser medium for which the angle of refraction will be 90° |
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Total internal reflection |
Occurs when the angle of incidence in the denser medium is bigger than the critical angle |
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Transverse wave |
The vibrations are at right angles to the direction the particle travels in |
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Longitudinal waves |
The vibrations are parallal to the direction in which the wave travels |
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Wavelength |
The distance between two crests (m) |
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Amplitude |
The max displacement from the baseline (m) |
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Frequency |
The number of complete cycles of a wave passing a point per second (Hz) |
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Period |
The time taken for a complete cycle of a wave (s) |
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Wavequation |
C=¥f |
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Reflection |
The rebounding of a wave/light off a surface |
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Refraction |
The bending of a wave as it passes from one medium to next (n=c1/c2) |
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Diffraction |
The spreading out of a wave in the space behind an obstacle or after going through an opening N¥=dsin0 |
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Interference |
When two or more waves meet and combine to form a resultant wave |
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Coherent sources |
Sources that are in phase and have the same frequency |
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Polarisation |
This is when the vibrations of a wave are in one plane only: only happens with transverse waves |
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Dispersion |
The separation out of white light into its constituent colours |
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Primary colours |
Red green blue-produce white light |
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Secondary colours |
Yellow cyan magenta-when primary colours are mixed in equal intensity |
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Complementary colours |
A primary and secondary colour mixing to give white light |
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Conductor |
A substance that allows charge to flow through it |
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Insulator |
A substance that does not allow charge to flow through it |
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Electric field |
A region where a charged particle experiences a force |
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Electric field strength |
The force per unit charge (E=F/q) |
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Potential difference |
Work done per unit charge (V=W/q) |
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Emf |
The work done in bringing unit charge around a complete circuit (V) |
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Capacitance |
The ratio of charge to potential difference (C=Q/V) |
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Coulomb's law |
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Electric current |
A flow of charge (A= 1 Coulomb per second) |
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Resistance |
The ratio of voltage to current R=V/I |
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Resistivity |
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Ohm's Law |
The current flowing through a wire is proportional to the potential difference across it V=IR |
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RCD |
Residual Current Device |
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MCB |
Miniature Circuit Breaker |
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Semiconductor |
Resistivity between that of a conductor and an insulator |
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Intrinsic vs Extrinsic conduction |
Conduction in a pure vs doped semiconductor |
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Thermionic emission |
Emission of electrons from the surface of hot metal |
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Electron-Volt |
The amount of energy gained by an electron being accelerated across a potential difference of 1 Volt |
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Photoelectric emission |
The emission of electrons from the surface of a metal when light of a suitable frequency falls on it |
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Photon |
A packet of electromagnetic energy (energy=hf) |
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Work function |
The minimum energy required by a photon to remove an electron from the surface of a metal by photoelectric emission (J or eV) |
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Threshold frequency |
The minimum frequency required for photoemission to occur |
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Einsteins photoelectric law |
Photon energy=work function +max kinetic energy of emitted electron |
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X rays |
High frequency photons of electromagnetic radiation |
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Atomic number |
Number of protons in the nucleus of an atom of that element |
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Isotopes |
Atoms that have the same atomic number but different mass numbers |
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Radioactivity |
The decay of a nucleus of an atom with the emission of one or more types of radiation |
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Activity |
The number of nuclei of a radioactive substance that is decaying per second |
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Bequerel |
The unit of activity = one radioactive disintegration per second |
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Law of radioactive decay |
The number of disintegrations per second is directly proportional to the number of nuclei present |
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Half life |
The time taken for half of the nuclei present to decay |
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Decay constant |
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Nuclear fission |
The splitting of a large nucleus into two smaller nuclei with the emission of neutrons and large amounts of energy |
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Chain reaction |
A self sustaining reaction where the release of one or more neutrons causes further fission |
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Nuclear fusiin |
The joining together of two light nuclei to form a larger nucleus with the emission of a large amount of energy |
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Leptons |
A point particle that does not experience the strong force |
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Hadron |
A particle made of three quarks= proton neutron |
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Meson |
A particle made of a quark and an anti quark (eg pion) |
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Anti-matter |
A particle with the same mass as a particle but opposite charge |
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Pair production |
A particle and it's anti particle are created from high energy (gamma-ray) photon (hf=2mc2) |
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Pair annihilation |
A particle and an anti particle are converted into two equal photons of energy (travelling in opposite directions) (2hf=2mc2) |
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Four forces in order of decreasing strength |
Strong nuclear force Electromagnetic Weak nuclear Gravitational |
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Thermistor |
A semiconductor whose resistance decreases rapidly with an increase in temperature |
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Holes |
When an electron breaks free from a covalent bond it leaves behind a gap in the atom from whence it came. |
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Intrinsic Conductor |
Conduction in a pure semiconductor with an equal number of holes moving from positive to negative and electrons moving in the opposite |
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Parallax |
The apparent movement of an object relative to another due to the motion of an observer |
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Magnification |
M=v/u |
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Short sighted |
A short sighted cannot bring far away objects into an object fixed with concave lens |
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Long sight |
Can't see up close objects fixed with convex lenses |
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Interference |
When waves combine to create a resultant wave |
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Pressure in a fluid |
P=pgh |
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Cathode Rays |
Streams of high speed electrons moving from the cathode |
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Kilowatt-Hour |
The amount of energy used by a 1000W appliance in one hour |
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LDR |
Light Dependent Resistor is a semiconductor whose conductivity is increased when light shines on it |
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Doping |
The adding of a small controlled amounts of certain impurities to a pure semiconductor to increase its conductivity |
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N-type semiconductor |
One which the impurity added produces more free electrons available for conduction (eg phosphorus) |
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P type semiconductor |
A semiconductor in which the impurity added produces extra hokes which are available for conduction (eg boron) |
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Intrinsic conduction |
Conduction in a pure semiconductor due to electrons move from negative to positive and an equal number of holes move in an opposite direction |
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Extrinsic conduction |
Increased conduction in a semiconductor due to the addition of impurities is called extrinsic conduction |
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Junction voltage |
The P. D. that exists across a p-n junction caused by holes and electrons moving across the junction when it was formed is called the junction voltage |
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Forward biased p-n junction |
Conducts current when positive terminal is connected to the P type |
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Reverse biased p-n junction |
Doesn't conduct current |
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Magnetic Field |
A region of space where magnetic forces can be felt in the direction of the force on the north pole if it were placed at that point |
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Magnetic Field Line |
A line drawn in a magnetic field so that the tangent to it at any point |
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Magentic Flux Density |
A vector whose magnitude is equal to the force that would be experienced by a conductor of length 1m carrying a current of 1 A at right angles to the field |
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The Ampere |
The current which, if maintained in two straight parallel conductors of infinite length, of negligible cross section and placed 1m apart in a vacuum would produce a force of 2x10(-7) N per metre length |
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Electromagnetic Induction |
Whenever the magnetic passing through a coil changes, an emf appears in the coil |
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Emf |
Electromotive Force |
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Faraday's Law |
The size of the induced emf is directly proportional to the rate of change of flux |
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Lenz's Law |
The direction of an induced current is always such as to oppose the change producing it |
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Electric Generator |
A device that converts mechanical energy to electrical energy |
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Mutual Induction |
When a changing magnetic field in one coil causes an induced emf to appear in a nearby coil |
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Self induction |
Whenever the current passing through a coil changes, the magnetic field surrounding that coil changes. This changing magnetic field induces an emf in the coil that opposes the changing current (back emf) |
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Transformer |
A transformer is a device used to change the value of alternating voltage |
