# G485 Key Definitions

A set of flashcards compiled of the key definitions from OCR physics A unit G485

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• Created by: abbiemca
• Created on: 20-04-16 23:31
Time Constant
The time taken for the potential difference (or current, or charge) to decrease to 1/e (37%) of its initial value.
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The induced e.m.f. is directly proportional to the rate of change of flux linkage
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Induced Nuclear Fission
A thermal neutron splits the nucleus int two smaller nuclei and fast moving neutrons
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Energy Level
Discrete energy of electrons in an atom
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Cosmological Principle
The universe is homogenous and isotropic on large scales
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Magnetic Flux
Magnetic flux density x area normal to the field
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Activity
Rate of decay of nuclei
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Electric Field Strength
Force per unit positive charge
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Hubble's Law
The recessional speed pf a galaxy is proportional to its distance from the Earth
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One coulomb per unit volt
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Capacitance
Charge per unit potential difference
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Torque of a Couple
One of the forces x perpendicular distance between the forces
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Photon
Quantum of electromagnetic energy
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Parsec
The distance from a base length of 1AU that subtends and angle of 1 arc second
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Decay Constant
The probability of decay of a nucleus per unit time
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Big Bang
The event which created the Universe
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Lenz's Law
Any induced current pt induced e.m.f will be established in a direction so as to produce effects which oppose the change that is producing it
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Coulomb's Law
The force between two electric charges is proportional to the product of the charges and inversely proportional to the square of the distance between them
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Electric Field
a region around a charged particle or object within which a force would be exerted on other charged particles or objects
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Weber (Wb)
One Weber is the unit of magnetic flux when a magnetic field of magnetic flux density 1 Tesla, passes at right angles through an area of 1m2.
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Tesla (T)
The unit of magnetic flux density, when a wire of length 1m carrying a current of 1A perpendicular to the field experiences a force of 1N
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Lightyear (ly)
The distance light travels in a vacuum in one year
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Fundamental Particles
Particles that cannot be broken down into smaller components
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Isotopes
Two nuclides (a nucleus with a distinct number of protons and neutrons) with the same number of protons but different numbers of neutrons
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Half-life
The average time taken for the activity of a radioactive source to decrease to one half of its original value OR the time taken for the number of radioactive nuclei to decrease by 1/2
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Binding Energy
The work done against the electrostatic force in assembling a nucleus from its individual protons and neutrons
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Astronomical Unit (AU)
The average distance from the centre of the Earth to the centre of the Sun
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## Other cards in this set

### Card 2

#### Front

The induced e.m.f. is directly proportional to the rate of change of flux linkage

### Card 3

#### Front

A thermal neutron splits the nucleus int two smaller nuclei and fast moving neutrons

### Card 4

#### Front

Discrete energy of electrons in an atom

### Card 5

#### Front

The universe is homogenous and isotropic on large scales