Week 4 Day 3 Advanced Physics

Question 1

Density of water

Answer 1

1 g/ml

1 g/cm³

1000 kg/m³

Question 2

Remember: Pressures are additive

Answer 2

P2 = P1 + p * g * h

On Dr. G’s formula sheet: ‘delta P’ = p * g * ‘delta h’

Question 3

Pascal’s Principle

Answer 3

When an external pressure is applied to a confined fluid, it is transmitted unchanged to every point within the fluid

P1 = P2, so

F1/A1 = F1/F2 at balance

Question 4

Hydrodynamics: Equation for flow rate.

Answer 4

Flow = Area (cross sectional area)(m2) * velcoity (m/s)

Flow = volume (m³) / time (sec)

Flow = Av = V/t

Question 5

Hydrodynamics: Equation of continuity (for an incompressible fluid)

Answer 5

fluid flows thru a tube with variable area sections

(think of fluid moving through the barrel a syringe and then into the needle)

A₁ * v₁ = A₂ * v₂

Question 6

Viscosity

Answer 6

measure of a fluid’s resistance to flow

Question 7

1 m³ = ___ L

Answer 7

1000 L

Question 8

What is a Coulomb?

Answer 8

SI unit of electrical charge; the magnitude of a charge

e = 1.602 x 10^-19 C

1 C = 6.24 x 10¹⁸ e

Question 9

How would you describe the movement of electrons?

Answer 9

Electric current

Current is measured in charge/time

1 Amp = 1 C/sec

Question 10

Describe an electrical conductor.

Answer 10

Conductors carry electrical current efficiently

Materials in which charges can move easily

*Most metals are generally good conductors*

Question 11

Describe an insulator.

Answer 11

Insulators resist carrying electrical current.

Materials in which charges cannot freely move.

*Most non-metals are insulators*

Question 12

The energy required to push electrons through a material is a measure of the _________ of the material.

Answer 12

resistance

Resistance is measured in Ohms

1 Ohm = 1 Volt/Amp

Question 13

Ohms law relates which 3 variables?

Answer 13

V = IR

Where:

V = voltage (force trying to move electrons)

I = current (Coloumbs/sec)

R = resistance (resistance against force ^)

The voltage driving electrons through a circuit is directly proportional to the volume of electron flow and the resistance of the medium to that flow.

Question 14

What is the the reciprocal of resistance?

Answer 14

Conductance (G)

measured in:

siemens (S) OR mho

G = 1 / R

G = 1 / Ohm

G = 1 / (Volt / Amp) becasue 1 Ohm = Volt / Amp

G = Amp / Volt

Question 15

What does this symbol represent?

Answer 15

The symbol for a resistor

Question 16

What does this symbol represent?

Answer 16

symbol for a battery

Question 17

What does this symbol represent?

Answer 17

symbol for a switch (SPST - single pole single throw)

i.e. simple on/off switch

Question 18

Equation for Resistors in Series

Answer 18

R_total = R₁ + R₂ + ……….R_n

the longer the length, the longer the resistance

Question 19

Describe a parallel circuit.

Answer 19

When resistors are connected in parallel, the current has more than one path that it can take. Thus, there will be a unique current that flows through each resistor independently.

1/R_total = 1/R₁ + 1/R₂ + ……1/R_n

Question 20

In terms of electical power, what is power?

Answer 20

Current times voltage

P (W) = I (A) * V (V)

where

W = watts

A = amp

V = Volt

Question 21

How to calcuate an energy unit.

Answer 21

energy = power * time

electrical energy is often expressed as kilowatt-hour (kWh)

Question 22

What is a semicondcutor?

Answer 22

materials with electrical conducting properties somewhere between those of insulators and conductors.

Question 23

P type semiconductuors

Answer 23

Group IV semi - metal (i.e silicon) doped with a Group III material (i.e. Boron)

Boron has a valence of 3 and so wherever a B sits in the crystal, some Si is missing an electron. This leaves a positive hole in the structure.

Question 24

Is silicon a good semicondcutor?

Answer 24

Pure crystalline silicon is a very poor conductor of electricity.

Question 25

N - type semiconductor

Answer 25

Group IV semi - metal (i.e. silicon) doped with a Group V material (i.e. arsenic)

Arsenic has a valence of 5, and so wherever an As sits in the crystal, there is an extra electron. This leaves a negative hole in the structure.

Question 26

What is a diode?

Answer 26

A diode is a p-type semiconductor bound to an n-type semiconductor.

A diode will conduct electricity in one direction, but not the other direction.

Question 27

Describe spectroscopy.

Answer 27

Involves shining light through, or reflecting light off, a material. Wavelengths of light that are absorbed by the material will not be transmitted

Question 28

What is a positron and what is a common use?

Answer 28

Positively charged electron

PET scan (Positron Emission Tomography)

Question 29

In terms of nuclides, (A) (Z) and (N) refer to:

Answer 29

(A) atmoic mass/mass number = (Z) + (N)

(Z) number of protons/atomic number

(N) number of neutrons

Question 30

Define radioactive decay.

Answer 30

Spontaneous process by which an unstable nucleus goes from a level of higher energy to one of lower energy.

Question 31

Describe alpha decay.

Answer 31

The emission of an alpha particle (helium nucleus) form the parent nucleus.

Energy is released in the form of kinetic energy of the escaping alpha particle and the recoiling daughter nucleus.

Question 32

T or F: Alpha declay usually involves very small nuclei.

Answer 32

False;

usually involves very large nuclei

Alpha particles (He ions) are big and don’t go far, so radiation is not a problem. (Unless the radioactive material in is your body already → then we have a BIG PROBLEM)

Question 33

Describe beta-minus decay.

Answer 33

Question 34

Describe B+ decay (positron decay)

Answer 34

Question 35

Does Gamma decay change the configuration of the nucleus?

Answer 35

No

The nucleus is in higher energy state and wants to go to a lower energy state. It does so by spitting out gamma rays.

This is how we can use I-123 for imaging without damaging the thyroid. Helpful in detecting metastases because the gamma rays emitted by I-123 will light are the area of mets on imaging (because thyroid cells are the only cells that take up Iodine)

Question 36

What is the half-life (t_1/2)?

Answer 36

Time it takes for half a radioactive material to decay

Question 37

What is the decay contsant?

Answer 37

The inverse of the half-life

Question 38

The decay of radioactive material follows which equation?

Answer 38

The shorter the half-life, the quicker it decays, and the greater the activity.

*Most medically relevant isotopes have short half-lives (20 min-20 days)*

Question 39

INFO CARD

Electromagnetic spectrum

Answer 39

Question 40

Which isotopes undergo B+ decay/positron decay?

Answer 40

C-11

N-13

O-15

F-18

Question 41

Beta minus decay

Answer 41

neutron → proton + e^- + v (antineutrino - dash above v) + energy

Question 42

B+ decay (positron decay)

Answer 42

proton → neutron + e⁺ + v (neutrino) + energy

Question 43

How does I-131 work to battle thyroid cancer?

Answer 43

Thyroid cells are the only cells with an Iodine transporter. If you inject I-131, the cells take up the I-131 and destroy the thryoid cells.

This is effective for metatstatic thyroid cancer

Question 44

Info Card

Gamma Knife

Answer 44

Question 45

Beer’s Law

Answer 45

Use in spectroscopy

Spectroscopy involves shining light through, or reflecting light off, a material. Wavelengths of light that are absorbed by the material will not be transmitted.

A = a * b * c

Absorbance (A) for a wavelength of light depends on the absorbtivity (a) of the material, the concentration (c) and the thickness (b)