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Physics As > Module 1 > Flashcards

Module 1 Flashcards

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1
Q

What is the definition of work function?

A

It is the minimum energy needed to remove an electron from the surface area of a metal.

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2
Q

Work function units

A

Joules (J)

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3
Q

What is the definition of threshold frequency?

A

It is the minimum frequency needed to remove an electron from the surface of a metal

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4
Q

What do the terms hf,  and Ekmax in the photoelectric equation?

A

hf - photon energy
 - work function
Ekmax - maximum kinetic energy of the photoelectron

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5
Q

What is the electron volt?

A

An electron volt (1 eV) is the energy gained by an electron moved across a potential difference of 1 volt.

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6
Q

How do you convert between electron Volts and Joules?

A

1eV = 1.6x10-19 J

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7
Q

What is excitation?

A

An (orbital) electron moves up from one energy level to another

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8
Q

What is an excited atom?

A

An atom in which an (orbiting) electron is raised up to a higher energy level

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9
Q

What is ionisation (in context of gas discharge tube)

A

When an electron is removed from an atom

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10
Q

What is ionisation energy?

A

The energy required to completely remove an electron from an atom in its ground state

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11
Q

What is the ground state of an atom?

A

The lowest energy state of an atom

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12
Q

What is fluorescence?

A

high energy (UV) photons are absorbed and lower energy photons (longer wavelength) are emitted in the visible part of spectrum

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13
Q

What is meant by wave particle duality?

A

particles (e.g. electrons, light) behave sometimes as particles and sometimes as waves

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14
Q

What is an experiment showing waves behaving as particles?

A

Photoelectric effect

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15
Q

What is an experiment showing particles behaving as waves?

A

Electron diffraction

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16
Q

Equation of momentum?

A

mass x velocity (p = mv)

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17
Q

What are the units of momentum?

A

kg ms-1

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18
Q

What is an electric current?

A

Rate of flow of charge

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19
Q

What is potential difference?

A

The work done (energy transferred) per unit charge

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20
Q

What is Ohm’s Law?

A

Current is directly proportional to potential difference, providing the temperature and other physical conditions remain the same

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21
Q

What is an ohmic conductor?

A

A conductor where I is directly proportional to V

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22
Q

What is a non-ohmic conductor?

A

A conductor where I is not directly proportional to V

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23
Q

What is the resistance of a voltmeter and ammeter?

A
  • Voltmeter resistance is very large ( or infinite)

- Ammeter resistance is very small (or zero)

24
Q

What do the terms , R, A and L mean in resistivity equation?

A
  •  is resistivity
  • R is resistance
  • L is length and
  • A is the cross-sectional area
25
Q

What is definition of resistivity?

A

Resistivity ρ is defined as ρ = RA/L where R is the resistance of material length L, and cross-sectional area A

26
Q

What are the units of resistivity?

A

 m

27
Q

What is superconductivity?

A

A material with zero resistivity

28
Q

What are the uses of superconductors?

A
  • MRI scanners
  • Maglev trains
  • Particle accelerators e.g. Large Hadron Collider
29
Q

What is the critical temperature?

A

The temperature at, and below which, a material has zero resistivity (or resistance)

30
Q

What is EMF?

A
  • actual energy provided by the battery (or cell) per unit charge
    OR
  • the terminal potential difference across the battery when no current is flowing
31
Q

What is internal resiitance

A
  • the hindrance to the flow of charge in the battery
    OR
  • the loss of potential difference per unit current
32
Q

What is “lost” potential difference?

A

potential difference dropped across the internal resistance of a cell (or battery)

33
Q

How does the resistance of a thermistor and wire change with increasing temperature?

A
  • Thermistor : resistance decreases as temperature increases

- Wire : resistance increases as temperature increases

34
Q

How does the resistance of and LDR changes with an increasing light intensity?

A

Resistance decreases with increasing light intensity

35
Q

What is the potential difference across a diode in forward bias?

A

A potential difference of 0.6V is dropped across a diode in forward bias

36
Q

What is the potential difference across cells in series and parallel?

A
  • In series, potential difference of each cell adds up

- In parallel, potential difference is the same

37
Q

What is the difference between a.c. and d.c current?

A
  • alternating current : direction of current is continually changing
  • direct current : current always flows in same direction
38
Q

What is the defintion of rms current and rms voltage?

A
  • rms current (Irms) : the equivalent dc current that produces the same heating effect in the same resistor
  • rms voltage (Vrms) : the equivalent dc voltage that produces the same heating effect in the same resistor
39
Q

What are the peak values (of current or voltage)?

A

The maximum current (or voltage) which is the same in either direction

40
Q

What are peak to peak values (of current or voltage)

A

the difference between the peak value one way and the peak value in the opposite direction (i.e twice the peak value)

41
Q

What is a time period?

A

Time for one complete oscillation

42
Q

What is an isotope?

A

an atom with the same number of protons but a different number of neutrons

43
Q

What is the equation for specific charge?

A

C kg-1

44
Q

What is the particle with the greatest specific charge?

A

electron

45
Q

What is an alpha particle, a beta particle and gamma particle

A

alpha particle : 2 protons and 2 neutrons (a helium nucleus)
beta particle : a fast moving electron
gamma particle : a high energy photon

46
Q

what are four different forces and their corresponding exchange particles?

A

strong force : gluon or pion
weak force : W particle
Electromagnetic force : virtual photon
Gravitational force : graviton

47
Q

What is pair production?

A

When a gamma photon changes into a particle and its corresponding antiparticle.

48
Q

What is annihilation?

A

When a particle and its antiparticle meet, they destroy each other and release 2 gamma photons

49
Q

What is antimatter?

A

Particles with the same rest mass but equal and opposite charge (if they are charged) as corresponding particle.

50
Q

What exchange particles transfer?

A

momentum; energy; force; sometimes charge (can only be transferred in a weak interaction)

51
Q

What are the differences between hadrons and leptons?

A
  • Hadrons : feel the strong force

- Leptons : do not feel the strong force

52
Q

What is the general quark composition of a baryon, anti baryon and a meson?

A

Baryon: qqq
Anti-Baryon: -q-q-q
Meson: q-q

53
Q

What do baryon’s decay into?

A

Protons

54
Q

What is the most stable baryon?

A

Proton

55
Q

What is conserved in strong and weak interactions?

A

All interactions: Energy, Momentum, Charge, Baryon Number, Lepton Number
Strong Force only : strangeness

56
Q

What is a strange particle?

A

A particle that contains at least q strange quark or anti-quark

57
Q

What is a chracteristic of a strange quark?

A

It has a strangeness of -1.

Physics As (2 decks)

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