# Fields, Particles and Frontiers of Physics Definitions

• Created by: roopa
• Created on: 11-04-15 13:29
Define Electric Field Strength
Force per unit positive charge
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Electric field strength, V/d
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Define magnetic flux density (B)
F = BIL sin(theta) where F is the force on a wire of length L carrying a current I at an angle theta to the field
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Define Tesla
1T is the magnetic flux density when a wire of length 1m, carrying a current 1A at a right angle to the field experiences a force of 1N
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Define the unified atomic mass unit u
1/12 of the mass of a carbon 12 nuclide
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Define Weber
The magnetic flux when a magnetic field of flux density one Tesla passes at right angles through an area of one square metre
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Define Magnetic Flux Linkage
Flux through one coil x number of coils
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State Faraday's Law of Induction
The magnitude of induced EMF is equal to the rate at which the magnetic flux is cut
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State Lenz's Law
The direction of any induced current is in a direction that opposes the flux change that caused it
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Define Capacitance
The charged stored per unit potential difference
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One Coulomb per Volt
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State the sum rule for capacitors in parallel
C = C1 + C2 + C3 + ...
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State the sum rule for capacitors in series
1/C = 1/(C1) + 1/(C2) + 1/(C3) + ...
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Define Time constant of a circuit
Time for the charge to have decreased to 1/e of its original charge, given by CR
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Define what is meant by an isotope of an element
Same number of protons, different number of neutrons
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Define Activity
The rate at which a source emits radioactive particles
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Define Becquerel
An activity of one particle per second
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Define Decay Constant
The probability of decay of a nucleus per unit time
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Define Half Life
The time taken for the activity of the source to decrease by one half. It is also the time taken for the number of radioactive nuclei to decrease by one half
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Define the binding energy of a nucleus
The energy required to separate all the nucleons of a nucleus to infinity
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Define Intensity
Power per cross sectional Area
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State Hubble's Law
The recession speed of a galaxy is directly proportional to its distance from Earth
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State the Cosmological Principle
On large scales, the Universe is: 1) Isotropic (The same in all directions) and 2) Homogeneous (has the same density)
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Define the Astronomical Unit
The average distance from the centre of the sun to the earth
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Define Parsec
Distance from a base length of 1AU that subtends an angle of 1 arc second
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Define light year
The distance travelled by an electromagnetic wave in one year
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Define Critical Density
The density required for the universe to have a flat geometery
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## Other cards in this set

### Card 2

#### Front

Electric field strength, V/d

### Card 3

#### Front

F = BIL sin(theta) where F is the force on a wire of length L carrying a current I at an angle theta to the field

#### Back ### Card 4

#### Front

1T is the magnetic flux density when a wire of length 1m, carrying a current 1A at a right angle to the field experiences a force of 1N

#### Back ### Card 5

#### Front

1/12 of the mass of a carbon 12 nuclide

#### Back 