Density of the magnetic field lines per unit area.

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Tesla

Magnetic flux density when a wire, length 1m, carrying a current of 1 ampere at right angles to the field experiences a force of 1m

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Magnetic flux (Φ)

Magnetic flux density x area perpendicular to the flux (Φ=BA)

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Weber

1Wb is the magnetic flux when a magnetic flux density of 1T passes through an area of 1m^2 at right angles

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Magnetic flux linkage (NΦ)

Magnetic flux x number of turns on the coil it passes through (measured in Weber turns)

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Lenz's Law

The induced e.m.f is always in such a direction as to oppose the change that caused it

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Faraday's Law

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

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Capacitance

Charge stored per unit potential difference

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Farad

1C of charge stored per volt

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Time constant of a circuit (CR)

Time taken for the charge remaining on a capacitor to fall to 1/e of its original value

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Proton number

Number of protons in a nucleus. Also known as the atomic number

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Nucleon number

Number of neutrons and protons in a nucleus. Also known as mass number

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Isotopes

Nuclides with the same number of protons but different numbers of neutrons

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Half-life

Average time taken for the number of undecayed atoms to halve

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Activity

Number of radioactive decays per unit time. Measured in Becquerels. A=λN

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Decay constant

The probability of radioactive decay λ=A/N

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Binding energy

Energy required to separate all the nucleons in the nucleus

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Binding energy per nucleon

Average energy required to remove a nucleon from the nucleus

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Intensity

Power per unit cross sectional area

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Astronomical Unit (AU)

Average distance from the earth to the sun 1AU= 1.496x10^11m

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Parsecs (pc)

1pc= 3.086x10^16m

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Light Years (ly)

1ly = 9.461x10^15m the distance that EM waves travel through a vacuum in 1 year

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Olber's Paradox

With an infinite number of stars in an infinite universe, no matter what direction you look you will always see a star in your line of sight. Therefore the night sky will be as bright as day sky

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Hubble's Law

The speed of recession of the galaxy is directly proportional to its distance from earth

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Critical Density

The average density of the universe above which the universe would collapse and below it would expand forever

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Cosmological principle

On a large scale the universe is homogeneous and isotropic, so doesn't have a centre

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Doppler effect

The change in wavelength caused by the relative motion between the wave source and the observer

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piezoelectric effect

The change in volume of certain crystals when a p.d is applied across them.

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Other cards in this set

Card 2

Front

Density of the magnetic field lines per unit area.

Back

Magnetic flux density (B)

Card 3

Front

Magnetic flux density when a wire, length 1m, carrying a current of 1 ampere at right angles to the field experiences a force of 1m

Back

Card 4

Front

Magnetic flux density x area perpendicular to the flux (Φ=BA)

Back

Card 5

Front

1Wb is the magnetic flux when a magnetic flux density of 1T passes through an area of 1m^2 at right angles

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