Module 1

Question 1

What is the definition of work function?

Answer 1

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

Question 2

Work function units

Answer 2

Joules (J)

Question 3

What is the definition of threshold frequency?

Answer 3

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

Question 4

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

Answer 4

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

Question 5

What is the electron volt?

Answer 5

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

Question 6

How do you convert between electron Volts and Joules?

Answer 6

1eV = 1.6x10-19 J

Question 7

What is excitation?

Answer 7

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

Question 8

What is an excited atom?

Answer 8

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

Question 9

What is ionisation (in context of gas discharge tube)

Answer 9

When an electron is removed from an atom

Question 10

What is ionisation energy?

Answer 10

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

Question 11

What is the ground state of an atom?

Answer 11

The lowest energy state of an atom

Question 12

What is fluorescence?

Answer 12

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

Question 13

What is meant by wave particle duality?

Answer 13

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

Question 14

What is an experiment showing waves behaving as particles?

Answer 14

Photoelectric effect

Question 15

What is an experiment showing particles behaving as waves?

Answer 15

Electron diffraction

Question 16

Equation of momentum?

Answer 16

mass x velocity (p = mv)

Question 17

What are the units of momentum?

Answer 17

kg ms-1

Question 18

What is an electric current?

Answer 18

Rate of flow of charge

Question 19

What is potential difference?

Answer 19

The work done (energy transferred) per unit charge

Question 20

What is Ohm’s Law?

Answer 20

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

Question 21

What is an ohmic conductor?

Answer 21

A conductor where I is directly proportional to V

Question 22

What is a non-ohmic conductor?

Answer 22

A conductor where I is not directly proportional to V

Question 23

What is the resistance of a voltmeter and ammeter?

Answer 23

• Voltmeter resistance is very large ( or infinite)

- Ammeter resistance is very small (or zero)

Question 24

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

Answer 24

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

Question 25

What is definition of resistivity?

Answer 25

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

Question 26

What are the units of resistivity?

Answer 26

 m

Question 27

What is superconductivity?

Answer 27

A material with zero resistivity

Question 28

What are the uses of superconductors?

Answer 28

- MRI scanners - Maglev trains - Particle accelerators e.g. Large Hadron Collider

Question 29

What is the critical temperature?

Answer 29

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

Question 30

What is EMF?

Answer 30

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

Question 31

What is internal resiitance

Answer 31

- the hindrance to the flow of charge in the battery OR - the loss of potential difference per unit current

Question 32

What is "lost" potential difference?

Answer 32

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

Question 33

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

Answer 33

- Thermistor : resistance decreases as temperature increases | - Wire : resistance increases as temperature increases

Question 34

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

Answer 34

Resistance decreases with increasing light intensity

Question 35

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

Answer 35

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

Question 36

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

Answer 36

- In series, potential difference of each cell adds up | - In parallel, potential difference is the same

Question 37

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

Answer 37

- alternating current : direction of current is continually changing - direct current : current always flows in same direction

Question 38

What is the defintion of rms current and rms voltage?

Answer 38

- 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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What is a time period?

Answer 41

Time for one complete oscillation

Question 42

What is an isotope?

Answer 42

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

Question 43

What is the equation for specific charge?

Answer 43

C kg-1

Question 44

What is the particle with the greatest specific charge?

Answer 44

electron

Question 45

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

Answer 45

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

Question 46

what are four different forces and their corresponding exchange particles?

Answer 46

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

Question 47

What is pair production?

Answer 47

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

Question 48

What is annihilation?

Answer 48

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

Question 49

What is antimatter?

Answer 49

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

Question 50

What exchange particles transfer?

Answer 50

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

Question 51

What are the differences between hadrons and leptons?

Answer 51

- Hadrons : feel the strong force | - Leptons : do not feel the strong force

Question 52

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

Answer 52

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

Question 53

What do baryon's decay into?

Answer 53

Protons

Question 54

What is the most stable baryon?

Answer 54

Proton

Question 55

What is conserved in strong and weak interactions?

Answer 55

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

Question 56

What is a strange particle?

Answer 56

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

Question 57

What is a chracteristic of a strange quark?

Answer 57

It has a strangeness of -1.