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(Name: _______Date: _______)The 14 Labs You Have to Know in Physics 30

In Alberta, the Government tells us that we have to perform 14 labs in Physics 30. All of these labs have the potential to be tested on the Diploma Exam, and at least a couple will make it into the skills based numerical response questions. Here’s a brief summary of each lab and a few things you might want to review, along with a couple of sample questions you might see something similar too.

Unit A: Momentum and Impulse

Lab 1: “Perform an Experiment to demonstrate the conservation of linear momentum”.

Remember:

· in order to apply this idea called the conservation of momentum, we have to assume the system is isolated. That means there are no outside forces acting on the system.

· the sum of the initial momentum of the system has to equal the sum of the final momentum of the system.

ex) 1D Momentum

Use the following information to answer the next 2 questions.

A group of students send two air track carts, A and B, with masses mA = 200 g and mB = 250 g, towards each other with equal speeds. The carts collide then rebound. The carts are outfitted with flexible bumpers in the collision. A summary of their findings is given below.

Before Collision

After Collision

Trial

Car A (cm/s)

Car B (cm/s)

’Car A (cm/s)

‘Car B (cm/s)

1

21.2

-21.2

-18.3

10.4

2

27.1

-27.1

-17.0

8.2

3

20.8

-20.8

-18.6

ab.c

1. Given the students’ results above, one could conclude that the air track and cart system is __i__ because __ii__.

The statements above are completed by the information in row

Row

i

ii

A.

isolated

momentum is conserved.

B.

non isolated

momentum is not conserved.

C.

elastic

momentum is conserved.

D.

inelastic

momentum is not conserved.

(Numerical Response)

(1. )The values of a, b, and c are _________.

(Record the three digits of your answer in the numerical-response section on the answer sheet.)

Unit B: Forces and Fields

Lab 2: “Perform and Activity to demonstrate methods of charge separation and transfer.”

Remember:

· In this context, only negative charge can move! Students will often refer to positive charge moving during charge separation. That would mean protons in the matter are moving, which is not the case. Only electrons may move freely through conductors.

· Electrons move from areas which are negative to areas which are positive, unless forced to do otherwise by a force.

· Transfer of charge by touching is conduction.

· Separation of charge without touching is induction.

· Transfer of charge can also be accomplished by induction and grounding (separating the charge in a conductor, then touching one end to ground to either remove or add electrons from the ground).

· Conductors allow electrons to spread out easily along their surface.

· Insulators do not allow electrons to spread out easily along their surface (but can still hold a charge).

ex) Electroscope Lab

Use the following information to answer the next question.

(A student brings a positively charged rod near to a negatively charged electroscope without making contact, as shown below.Describing Terms and Phrases1.positive2.negative 3.towards4.away from5.induction6.conduction7.spread out8.move closer together9.not change)


(2. )In the experiment described above, __a__ charge will move __b__ the positively charge rod through the process of __c__. As a result, the gold leafs at the bottom of the electroscope will __d__ when compared to their original position.

The numbers of the terms and phrases above that best complete the blanks in the order a, b, c and d are ___, ___, ___ and ___.

(Record the four digits of your answer in the numerical-response section on the answer sheet.)

Lab 3: “Perform an experiment to demonstrate the relationships among magnitude of charge, electric force and distance between point charges.”

Remember:

· This outcome is talking about testing Coulomb’s Law, . This will typically call for curve straightening and is a good example of graphical analysis in Physics 30.

· The electric force is inversely proportional to the square of the radius (inverse square relationship).

ex) Coulomb’s Law and Curve Straightening

Use the following information to answer the next 6 questions:

In an experiment designed to evaluate Coulomb’s Law, two identical, equally charged pith balls are brought into proximity with one another, as shown to the right. The pith ball on the left is attached to an insulated stand; the pith ball on the right is suspended freely on an insulated string. The mass of each pith ball is 2.5 g.

Students varied the distance between the pith balls (r) and measured the angle of displacement of the suspended pith ball (θ). From this data, the electric force between the pith balls can be calculated.

A table of the students’ findings is shown below:

separation, r (m)

angle of displacement, θ (degrees)

electric force, (N)

0.080

79

0.12

0.12

66

0.056

0.22

34

0.017

0.25

28

0.013

0.32

18

0.0079

2. An equation that correctly gives the electric force, , from the angle of displacement, θ, and the mass of the suspended ball, m, is

A.(mg) x tan(θ)

B.(mg) x sin(θ)

C.(mg) ÷ tan(θ)

D.(mg) ÷ cos(θ)

Use the following additional information to answer the next question.

The students create a graph of the electric force,, vs. the inverse square of the radius, r-2. The straight line graph is shown below.


(3. )On the linear line of best fit for the graph above, the value of the slope is a.bc x 10-d Nm2. (3. )The values of a, b, c and d are ___, ___, ___ and ___.



(4. )

The experimental value of the charge on either sphere based on the slope of the graph is a.bc x 10-d C. The values of a, b, c and d are ___, ___, ___ and ___.


Lab 4: “Perform an experiment to demonstrate the effect of a uniform magnetic field on a current-carrying conductor.”

Remember:

· This outcome is talking about testing .

· The magnetic field must be perpendicular to the current and therefore the length of wire in order to result in a force.

ex 1) Determining Magnetic Field Strength Lab

(A group of students conduct a lab to determine the magnetic field strength of a magnet. The students place a wire of length L = 78 cm across a conducting stand fixed to a digital weigh scale which is insulated from the stand. A current is passed through the wire resulting in different readings on the scale. A summary of the students’ findings is given below:current, I (A)mass read out (g)05.000.3754.750.6254.501.0004.251.6253.75*Note: the apparatus is zeroed to negate the mass of the conducting stand.)


(Variables1.mass of wire2.read out of mass from digital weigh scale3.length of wire4.current5.force of gravity6.force of magnetism)


(5. )The numbers of the variables above which represent a controlled, manipulated and responding variable, respectively, are ____, ____, and ____.



In order to determine the magnetic field strength, the students created a graph of mass readout versus current in the wire. A plot of the data is shown below.


(6. )The magnetic field strength of the magnet in the lab is a.bc x 10-d T. The values of a, b, c and d are ___, ___, ___ and ___.


ex 2) Determining Earth’s Magnetic Field Strength Lab (This question is the graphing question from the Physics 30 2010–2011 Information Bulletin).



(7. )The y-intercept of the line of best fit, expressed in scientific notation, is a × 10–b (no units). You will need to record the values of a and b.

Using the slope, the experimental value of the magnitude of BEarth, expressed in scientific

notation, is e.f × 10–g T. You will need to record the values of e and f.

The values of a, b, e, and f are _____, _____, _____, and _____.

a b e f

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Lab 5 “Perform an experiment to demonstrate the effect of a uniform magnetic field on a moving conductor.”

Remember:

· This outcome is talking about induced current: current produced when a conductor moves through a magnetic field or vice versa.

· The direction of the field and current must have a perpendicular component in order to produce a force.

· You will often have to use Lenz’ Law here: the direction of the induced current is always such that it will induce a magnetic field to oppose motion.

· This is a good place to test the 3rd left hand rule: the way I do it has the thumb as the direction of the current, the index finger the direction of the magnetic field and the middle finger the direction of the magnetic force.

· When I do induction with the 3rd LHR, I just apply it to one electron in the conductor, determine the force on that electron and then work out the current from there.

ex) Lenz’s Law in a Solenoid

(A group of students conduct an experiment to determine the direction of induced current flowing through a solenoid. The experimental design is shown below:Directions and Poles1.left2.right3.up4.down5.into the page6.out of the page7. North8.South)Use the following information to answer the next question.


(8. )

In the experiment if the students moved the bar magnet _____ the solenoid will induce a ______ pole and current will flow ______ through the voltmeter.

One correct combination of numbers of directions and poles that complete the blanks above is ___, ___ and ___.

(Record all three digits of your answer in the numerical-response section on the answer sheet.)

Unit C: Electromagnetic Radiation

Lab 6: “Perform experiments to demonstrate reflection at plane and uniformly curved surfaces.”

Remember:

· The two principle lines produced by curved mirrors: one goes parallel to the principal axis, then reflects through the focal point; the second goes through the focal point then reflects parallel to the principal axis.

· This lab tests the relationship .

· The mirror conventions: distances are positive when measured in front of the mirror and negative when measured behind the mirror, heights are positive when erect and negative when inverted.

ex) A concave mirror lab.

(To investigate the images formed by concave mirrors a pair of students take turns holding a large, concave mirror and try standing different distances from the mirror. The mirror has a focal length of f.)Use the following information to answer the next question.

3. The student looking into the mirror would see his image inverted when he is __i__ and would see his image as erect when he is __ii__.


Row

i

ii

A.

right of f

left of f

B.

left of f

right of f

C.

at f

right of f

D.

right of f

at f

Lab 7: “Perform an experiment to determine the index of refraction of several substances.”

Remember:

· this lab is testing Snell’s Law, .

ex) Determining Index of Refraction of Water.


A group of students performs an experiment to calculate the refractive index of water. The students collect the following data and construct the following graph:

4. In the analysis of the lab, the students determine the slope of their graph. In order to find the index of refraction of water, the students should then

a) reciprocate their slope to give nwater.

b) take the inverse sine of their slope to give nwater.

c) square root their slope to give nwater.

d) do nothing: the slope is equal to nwater.

Lab 8: “Conduct an investigation to determine the focal length of a thin lens and curved mirror.”

Remember:

· The lens conventions: converging (convex) lens have positive focal lengths, diverging (concave) lens have negative focal lengths, distances are positive when measured in front of the mirror and negative when measured behind the mirror, heights are positive when erect and negative when inverted.

· This lab tests the relationship .

ex) Determining the Focal Length of a Lens Lab (this example taken from the 2010-2011 Bulletin)


(Some physics students do an experiment to find the focal length of a converging lens. They set up an optical bench and measure the image distance as a function of the object distance.)


(9.)The slope of the line is –a.b. You will need to record the values of a and b.

Using the y-intercept, the experimental value of the focal length of the lens, expressed in units of centimetres, is ef cm. You will need to record the values of e and f.

The values of a, b, e, and f are _____, _____, _____, and _____.

a b e f

(Record all four digits of your answer in the numerical-response section on the answer sheet.)

Lab 9: “Observe the visible spectra formed by diffraction gratings and triangular prisms.”

Remember:

· prisms form a continuous spectrum the orders the light ROY G BIV.

· diffraction gratings form many small spectrums to the right and left of the light source. Spectrums to the left are in the order (read left to right) ROY G BIV, spectrums to the right are in order (read left to right) VIB G YOR.

ex) Observing Spectrums Lab

(A student looks through a mystery box. The box contains some piece of optical equipment. Below is a diagram of what the student observed. (Note: to those of you without colour, the letters correspond to the names of the colours of light the student sees.))Use the following information to answer the next question.

5. The optical device the student was looking through was a

A.prism

B.diffraction grating

C.convex lens

D.concave lens

Lab 10: “Perform an experiment to determine the wavelength of a light source in air or in a liquid, using a double-slit or a diffraction grating.”

Remember:

· This lab tests the principle of diffraction of light and shows light’s wave properties.

· Waves diffract when passing through at least two openings around the same size as the wavelength of the wave.

· This outcome is challenging because there are two equations with many variables all being distances measured in metres:

· , where d is the distance between the slits and n is the number of the antinode you are determining the wavelength of and θ is the angle between the central bright spot and the antinode you’re interested in. This formula works in all situations! However, as θ is usually very small, it is impractical to measure in many lab situations…

· Therefore, we will often use , where x is the distance between the central antinode and the antinode you’re interested in and L is the distance between the slits and the screen where the interference pattern is produced. This is often called the small angle approximation formula because it only works for angles which are small, where

tanθ ≈ sinθ, x << L or θ < 10°.

ex) Measuring the wavelength of a discharge tube (this example taken from the 2010-2011 Bulletin)

Use the following information to answer the next two questions.

(A group of students is given a low-pressure helium gas-discharge tube, a high-voltage power supply with wire leads, a retort stand with clamps for holding the discharge tube, a diffraction grating, and two metre sticks.The group clamps the gas-discharge tube into a vertical position and connects it to the powersupply. A metre stick is placed horizontally, directly in front of the discharge tube so that the tube is lined up with the 50.0 cm mark. The second metre stick is placed perpendicular to the first metre stick, directly in line with the center of the discharge tube. Finally, a diffraction grating is placed 100 cm from the low-pressure helium gas-discharge tube. The diagram below illustrates the set-up.Perspective View of Student ApparatusWhen the power supply is switched on, an electric current passes through the gas, and the tube emits a pinkish-yellow light.Using a diffraction grating etched with lines that are spaced 4.35 × 10–6 m apart, the studentsobserve a series of brightly coloured spectral lines to the right of the location of the discharge tube, as shown below.The yellow spectral line is significantly brighter than the other lines.)

6. If the students replace the diffraction grating with one that has more lines per millimetre etched onto it, then the red spectral line will be observed i the discharge tube. In order to keep the red spectral line in approximately the same position as in the original observations, the students would have to move the diffraction grating ii the discharge tube.


Row

i

ii

A.

closer to

closer to

B.

closer to

farther from

C.

farther from

closer to

D.

farther from

farther from


(10.)The wavelength of the yellow spectral line for helium, based on the students’ observations, expressed in scientific notation, is a.bc × 10–d m. The values of a, b, c, and d are _____, _____, _____, and _____.


Lab 11: “Perform an experiment to verify the effects on an interference pattern due to changes in wavelength, slit separation and/or screen distance.”

Remember:

· This outcome is talking about checking the formulas and to see if they work in a qualitative way, i.e. if you increase the d, what happens to the wavelength of the diffracted light?

ex) Red vs. Green vs. TV Remote Lasers

Use the following information to answer the three questions.

(A group of students perform an experiment to investigate the effect of different diffraction gratings on the interference pattern produced by three different EMR sources: a red LASER, a green LASER and a TV remote (which is invisible to the naked eye but can be viewed through a digital camera).The students first determined the value of x for a particular grating with a distance between the slits of d1 and the red LASER. They then change the grating to one with a different number of lines per slit, d2. Their results are below. EMR Sourcex value for d1x value for d2red LASER345 mm525 mm)7. In the students’ lab, the controlled variable was __i__, the manipulated variable was __ii__ and the responding variable was iii__.


Row

i

ii

iii

A.

λ

x

d

B.

d

λ

x

C.

d

x

λ

D.

λ

d

x


8. If a green LASER were to replace the red LASER, the value of x would be expected to

A.increase

B. decrease

C.remain the same

D.not diffract

9. Students find that when the TV remote is compared to the red LASER, the value of x has increased. A valid assumption is that the TV remote emits EMR in the range of

A.ultraviolet light

B.green light

C.red light

D.infrared light

Unit D: Atomic Physics

Lab 12: “Perform an experiment, or use simulations, to determine the charge-to-mass ratio of the electron.”

Remember:

· This is the experiment J.J. Thomson performed to determine that Cathode Ray Tubes were actually electrons and that electrons existed as the smallest particle of matter (at the time).

· In his experiment, Thomson used electric fields to accelerate the electrons and magnetic fields to select the velocity (the two forces were equal here), then curve it in part of a circle (only the magnetic or electric force were used for this). This allowed him to set the and determine the charge to mass ratio, .

ex) Thomson’s q/m experiment

Use the following information to answer the next three questions.

(In his charge to mass (q/m) experiment, J.J. Thomson used a cathode ray tube similar to the one shown in the diagram below.The cathode ray tube had two main regions: two vertical parallel plates with a potential difference put across them (labeled A) and a second set of horizontal plates which created an electric field in the same region as a magnetic field (labeled B). The dotted line indicates the movement of the cathode rays. Vector Directions1.←2.→3.↑4.↓5.• (out of the plane of page)6.x (into the plane of the page))


(11.)When the cathode ray particle is in region A, the direction of the electric field and electric force are, respectively, ___ and ___; when the cathode ray particle is in region B, the direction of the electric field and electric force are, respectively ___ and ___.

Record the numbers of the Vector Directions above that best complete the statement.



(12.)The parallel plates in region A have a potential difference of 2.50 x 104 V across them. When the cathode ray particles reach region B, they enter an electric field of 6.0 x 105 N/C. If the particle passes through region B undeflected, the value of the magnetic field in region B must be a.bc x 10-d T.


Lab 13: “Observe line-emission and line-absorption spectra.”

Remember:

· This is testing the Bohr Model of the atom: when electrons absorb EMR, they jump up energy levels, when electrons emit EMR, they jump down.

· The energy levels are set for each element at particular, unchanging and unique values, thus the differences in energies between each orbital is unique for each element, as are the wavelengths of light the elements emit or absorb.

This outcome is similar to

Lab 14: “Observe the representative line spectra of selected elements.”

(A student observes the following emission spectrum of a hypothetical LD-atom through a digital camera:The student hypothesizes that the three emission lines shown above correspond to an atom with three energy levels, n1, n2, and n3.)ex) Line spectrum emission.


(13.)The numbers of the emission lines that match the selected energy transitions are

__________________

n3 n1n3 n2n2 n1


Performing a Linear Regression on the TI-84 Plus Calculator

This method will allow you to quickly take data points that form a line when graphed and calculate their slope. In physics, this can be very helpful when finding velocities or accelerations from graphs of distance vs. time or velocity vs. time.

(4. Use the WINDOW functions as needed to see your graph. The dots should form a rough line. )

(3. You can now view your graph. Press Y=, clear out any old equations you might have entered in, then scroll up to Plot 1 and press ENTER until it turns black. ) (2. This is the list menu. Enter the values of x in L1 and y in L2. To clear out a large number of old data points, scroll up to the L1 or L2 title, press CLEAR then ENTER.) (1. From the main screen, press STAT, then press ENTER on Edit…)

(8. …or while in the Y= screen by pressing VARS, scrolling down to Statistics…, pressing ENTER then scrolling right to EQ and hitting ENTER on RegEq. If all went well, the plotted points should match the line.) (7. This is your regression equation. The value of “a” is the slope, the value of “b” is the y-intercept.To see how this equation matches your data, enter it into the Y= menu by hand…) (6. If you have no other data entered into your calculator, you can just press ENTER. If you have other data in the Stat Plot menu, enter in (L1, L2) behind the LinReg(ax+b) command, then press ENTER.) (5. Press STAT, then scroll one right to CALC, scroll down and press ENTER on LinReg (ax+b). This is the Linear Regression feature.)

electric force vs. inverse square of radius

156.2569.44444444444457120.66115702479339169.7656250.120000000000000025.6000000000000001E-21.7000000000000001E-21.2999999999999998E-27.9000000000000164E-3

r-2 (m2)

electric force (N)

Mass Readout vs. Current

00.375000000000000440.62500000000000111.62554.754.54.253.75

Current (A)

Mass Readout (g)

sin θi vs sinθr

sin i00.121869343405147490.275637355816998550.406736643075800320.461748613235033910.551936985312056260.636078220277763950.7193398003386516400.173648177666930410.342020143325669770.50.642787609686540920.766044443118980790.866025403784440040.93969262078590832

sin(θr)

sin(θi)

23

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