A-Level Physics G485 Flashcards Preview

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Flashcards in A-Level Physics G485 Deck (169)
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Define Electric Field Strength

Electric field strength at a point in space is the force per unit positive charge


Define Magnetic Flux Density

a measure of the strength of a magnetic field at a given point, expressed by the force per unit length on a conductor carrying unit current at that point.


Define Tesla

One Tesla is the uniform magnetic flux density which, acting normally to a long straight wire carrying a current of 1 ampere, causes a force per unit length of 1Nm-1 on the conductor.


Define Magnetic flux

magnetic flux = magnetic flux density x area (perpendicular to field direction)
B x A (normal to B). Magnetic flux=magnetic field x Area


Define The Weber

One Weber is equal to one Tesla metre²


Define Magnetic Flux Linkage

The change of magnetic flux linkage is equal to the product of the change in magnetic flux and the number of turns N of a conductor involved in the change in flux


Define Capacitance

Capacitance = charge per (unit) potential differences
Ratio of charge to potential for a conductor


Define The Farad

coulomb per volt
A farad is the charge in coulombs which a capacitor will accept for the potential across it to change 1 volt


Define The Time Constant Of A Circuit

Time for the charge to have decreased to "1/e" of its initial charge


Define Proton Number

The number of protons found in the nucleus of an atom


Define Nucleon Number

The mass number, the sum of the number of neutrons and protons in an atomic nucleus


Define Isotopes

Isotopes are different forms of the same element which have the same number of protons but different numbers of neutrons in their nuclei


Define Activity (Radioactivity)

Spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay


Define The Decay Constant

The probability of decay of a nucleus per
unit time
Reciprocal of decay time


Define Half Life

The half-life of a radioactive nuclide is the time taken for the number of un-decayed nuclei to be reduced to half its original number


Define Binding Energy

The energy equivalent of the mass defect of a nucleus. It is the energy required to separate to infinity all the nucleons of a nucleus


Define Binding Energy Per Nucleon

Binding energy per nucleon is defined as the total energy needed to completely separate all the nucleons in a nucleus divided by the number of nucleons in the nucleus


Define Intensity

Power per unit area(W/m²)


Define The Distance Measured In Astronomical Units (AU)

The astronomical unit is defined as the radius of the circular path round the sun followed by a body in 365.25 days


Define The Distance Measured In Parsecs (pc)

Distance from a base length of 1 AU that subtends an angle of 1 (arc) second


Define The Distance Measured In Light-Years (ly)

The distance travelled by electromagnetic radiation (light) in one year


Define Critical Density

The average density of the universe

  •  Above which the universe will collapse (closed universe)
  • Below which the universe will expand forever (open universe)
  •  If the density is equal to the critical universe get a flat universe.


State that electric fields are created by electric charges

Electric charges exert forces on each other when they are a distant apart. An electric field is a region of space where a stationary charge experiences a force


State and use Fleming’s left-hand rule to determine the force on a current conductor places at right angles to a magnetic field.

If the first two fingers and thumb of the left hands are placed at right angles then the first finger is in the direction of the field, the second in the direction of the current and the thumb in the direction of motion


State and use Faradays Law of electromagnetic induction

Induced e.m.f is proportional to the rate of change of (magnetic) flux


State and use Lenz’s law

The direction of the induced e.m.f is such as to cause effects to oppose the change producing it


State and use the equation for the total capacitance of two or more capacitors in parallel

C= C1+C2+C3.......


State and use the equation for the total capacitance of two or more capacitors in series

1/Ct =1/C1+1/C2+1/C3 ......


State the quantities conserved in a nuclear decay

The charge, the total number of neutrons and protons, total energy, the total momentum of the system and the total lepton number.


State that there are two types of β decay

β- decay produces an emission of electrons. (Electron) antineutrinos are produced.

A β- particle IS an electron.


β+ decay produces an emission of positrons. (Electron) neutrinos are produced.

A β+ particle IS a positron.