Week 4 Day 3 Advanced Physics Flashcards
Density of water
1 g/ml
1 g/cm3
1000 kg/m3
Remember: Pressures are additive
P2 = P1 + p * g * h
On Dr. G’s formula sheet: ‘delta P’ = p * g * ‘delta h’
Pascal’s Principle
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
Hydrodynamics: Equation for flow rate.
Flow = Area (cross sectional area)(m2) * velcoity (m/s)
Flow = volume (m3) / time (sec)
Flow = Av = V/t
Hydrodynamics: Equation of continuity (for an incompressible fluid)
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
Viscosity
measure of a fluid’s resistance to flow
1 m3 = ___ L
1000 L
What is a Coulomb?
SI unit of electrical charge; the magnitude of a charge
e = 1.602 x 10-19 C
1 C = 6.24 x 1018 e
How would you describe the movement of electrons?
Electric current
Current is measured in charge/time
1 Amp = 1 C/sec
Describe an electrical conductor.
Conductors carry electrical current efficiently
Materials in which charges can move easily
*Most metals are generally good conductors*
Describe an insulator.
Insulators resist carrying electrical current.
Materials in which charges cannot freely move.
*Most non-metals are insulators*
The energy required to push electrons through a material is a measure of the _________ of the material.
resistance
Resistance is measured in Ohms
1 Ohm = 1 Volt/Amp
Ohms law relates which 3 variables?
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.
What is the the reciprocal of resistance?
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
What does this symbol represent?
The symbol for a resistor
What does this symbol represent?
symbol for a battery
What does this symbol represent?
symbol for a switch (SPST - single pole single throw)
i.e. simple on/off switch
Equation for Resistors in Series
Rtotal = R1 + R2 + ……….Rn
the longer the length, the longer the resistance
Describe a parallel circuit.
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/Rtotal = 1/R1 + 1/R2 + ……1/Rn
In terms of electical power, what is power?
Current times voltage
P (W) = I (A) * V (V)
where
W = watts
A = amp
V = Volt
How to calcuate an energy unit.
energy = power * time
electrical energy is often expressed as kilowatt-hour (kWh)
What is a semicondcutor?
materials with electrical conducting properties somewhere between those of insulators and conductors.
P type semiconductuors
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.
Is silicon a good semicondcutor?
Pure crystalline silicon is a very poor conductor of electricity.
N - type semiconductor
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.
What is a diode?
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.
Describe spectroscopy.
Involves shining light through, or reflecting light off, a material. Wavelengths of light that are absorbed by the material will not be transmitted
What is a positron and what is a common use?
Positively charged electron
PET scan (Positron Emission Tomography)
In terms of nuclides, (A) (Z) and (N) refer to:
(A) atmoic mass/mass number = (Z) + (N)
(Z) number of protons/atomic number
(N) number of neutrons
Define radioactive decay.
Spontaneous process by which an unstable nucleus goes from a level of higher energy to one of lower energy.
Describe alpha decay.
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.
T or F: Alpha declay usually involves very small nuclei.
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)
Describe beta-minus decay.
Describe B+ decay (positron decay)
Does Gamma decay change the configuration of the nucleus?
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)
What is the half-life (t1/2)?
Time it takes for half a radioactive material to decay
What is the decay contsant?
The inverse of the half-life
The decay of radioactive material follows which equation?
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)*
INFO CARD
Electromagnetic spectrum
Which isotopes undergo B+ decay/positron decay?
C-11
N-13
O-15
F-18
Beta minus decay
neutron → proton + e- + v (antineutrino - dash above v) + energy
B+ decay (positron decay)
proton → neutron + e+ + v (neutrino) + energy
How does I-131 work to battle thyroid cancer?
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
Info Card
Gamma Knife
Beer’s Law
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)
