PHYS 320 Full Course - DevryOnlineHelp.com
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# PHYS 320 Full Course - DevryOnlineHelp.com

## PHYS 320 Lab 30 Magnetic Fields

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Experiment 1: Exploring Magnets

Questions

1. The stack of magnets works as one big bar magnet. Do the poles change when you divide the magnet into pieces?

2. In step 3, do both sides of the magnet attract the metal surface? Explain how a single magnet can repel the rest of the stack, but still stick to the other surface.

3. How does the magnet attract something that is originally non-magnetic?

4. Does the bolt become magnetized when in contact with one of the permanent magnets? How is this similar to the electric charge in a conductor?

Experiment 2: Levitating Magnets

1.Draw the results of steps 2 through 4 in the space below. Why are the magnets spaced in such a way? Label the north and south poles of each single magnet.

2.Draw the result of step 5 in the space below. Was the force between the magnets enough to keep the large group levitated?

3. Label the north and south poles of each magnet in your drawing above. Add in the magnetic field lines between magnet groups.

4.What does this experiment demonstrate about the relative strengths of the forces due to gravity and magnetism? 1

Experiment 3: Magnetic Field Lines

1.Describe the direction of the compass needle as you moved it around the bar magnet. Which direction did the needle point? How far away did the compass have to be?

2.The compass points toward Earth’s geographic North Pole—which is actually the Earth’s magnetic South Pole. Knowing this, which end of the magnet is the South Pole and which is the North Pole?

3.How do the iron filings compare to your predicted magnetic field lines?

4.Describe the direction of the magnetic field lines between two attracting magnets compared to two repelling magnets.

5.Is it possible to distinguish the north and south poles of the stack of magnets by looking at the magnetic field lines they produce?

Experiment 4: Building an Electromagnet

Questions

1.In what direction will the magnetic field travel through the nail? Predict this using the right hand rule and the direction of current flow (positive terminal to negative on the battery).

2.From your answer in Question 1, which end will be the north pole of your electromagnet, and which one will be the south? Remember, the direction of the magnetic field is outward from the North Pole and inward toward the South Pole.

3.Draw a sketch of the magnetic field lines for your electromagnet.

4.Were your predictions about the north and south poles of the magnet correct? How do you know?

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Experiment 1: Drawing Ray Diagrams 5.06 14.

Questions

1. Use the lens equation to predict the image distance for each case—you will have to rearrange the equation to solve for si. Remember, f is positive for a concave mirror, negative for a convex mirror, and positive for a converging lens. Write down whether the image is real or virtual in each case.

2. Measure the distance from the lens to the image on your diagrams—do your predicted image distances match what you got using the lens equation?

3. The magnification for each case is found by taking the image height divided by the object height, or m = hi / ho . For an upright image, m is positive, and for an inverted image, m is negative. What is the magnification in each of your cases?

Experiment 2: Exploring Mirrors

Questions

1. Is your image in the convex mirror a virtual image or a real image? How do you know?

2.Did this mirror give you a good view of a lot of objects to either side of you? Where have you seen mirrors like this used, and what do you think makes them useful?

3.When you held the concave mirror close to you, was the image real or virtual? How do you know?

4.How did the magnifications compare for each mirror (i.e. how big was your image in each case)?

5.What happened to your image in the concave mirror as you moved it gradually away?

6.Based on what you observed, give an estimate for the focal length of the concave mirror.

Experiment 3: Exploring Lenses

Questions

1. Did objects appear larger or smaller looking through the concave lens? What kind of image do you see through this lens, and how do you know?

2. Did objects appear larger or smaller looking through the convex lens? What kind of image is this, and how do you know?

3.What happened when you moved the lens too far away from the object? Knowing the difference between real and virtual images, explain why this happens. (Go back to Exercise 1, and note the difference between the two convex lens diagrams you drew).

4.What kind of image did you view on the screen in Procedure 2? How do you know?

5.Explain why you need the screen to view the image in this case.

6.Is it possible to view a virtual image with a screen? Why or why not?

7.How is the orientation of the image (right-side-up or upside-down) helpful for determining the type of image? Take a look at Figure 5 for some help.

Experiment 4: Mirror Images

Questions

1. As you moved the flashlight closer to the mirror, what generally happened to the image distance?

2. What was the average focal length you measured for the mirror?

3. What would the image distance si be for an object 10 m away? (Hint: you can approximate that a very far object is “at infinity”).

4.Where would the image be located if you placed the flashlight 10 cm away? Would you be able to detect this image using the same method?

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Experiment 1: Conduction

Questions

1. Explain how the handle of a spoon gets warm even though it is not in direct contact with the hot water.

2. Looking at the list that you made, which material would you guess has the highest conductivity? Which should have the lowest?

3. Compare your list to the provided conductivity values above. Were your predictions correct?

4. What is the conductivity of air? Comparing this to other values on the conductivity chart, why do you think double-paned windows (which have air in between two layers of glass) are a good home investment if you do not want a high heating and cooling bill?

Experiment 2: Convection Experiment

Questions

1. What happened when the card was removed with the warm water jar on top? Can you explain why this happens?

2. What happened differently with the cold water jar on top? Explain what happens using your knowledge of the types of heat transfer.

3. What happens to the temperature of the jars in the second case?

4. Are there any other types of heat transfer apparent in this experiment?

Questions

1. In which cup did the ice melt the fastest? In which one did the ice melt the slowest?

2. Summarize the rate of temperature change for each cup.

3. Explain your results in terms of heat transfer concepts. In other words, which cup(s) protected the ice from conduction, convection, and radiation? How did they achieve this?

4.Comment on how your particular experimental conditions affected your experiment. For instance, on a very sunny day the effects of radiation are significant compared to a cloudy day and the cup with foil might show less drastic improvement over the cup with only a lid.

5. Explain why a foam cup offers good insulation while at the same time is a lightweight material.

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## PHYS 320 Lab 20 Temperature and Heat | DeVry Online Help

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Experiment 1: Thermometer

Questions

1. What happened to the straw water level when you ran the warm water over the bottle? Why does this happen?

2. What happens to the water level when you placed the thermometer in a cold setting? Why does this happen?

3. What do your answers demonstrate about the air pressure inside the bottle? Why is it important that the top of the bottle is sealed around the straw?

4. Would your thermometer work if the bottle was completely full of water? How do you think mercury thermometers work without air (think about the diameter of a mercury thermometer vs. the diameter of your straw)?

Experiment 2: Thermal Expansion and Contraction

Questions

1. What happened to the temperature of the rubber band after stretching it? Does this indicate that stretching the band adds energy or subtracts energy from the rubber? Explain this in terms of work done on and by the band.

2. What happened when you heated the center of the rubber band?

3. Create a hypothesis explaining what is happening to the molecules of the rubber as it is heated and cooled.

Experiment 3: Specific Heat

Questions

1. The heat lost by the hot bolt is equal to the heat gained by the water in the calorimeter. Use the equations provided above and what you know about heat to solve for the specific heat (C1 ) of the steel.

2. What is the specific heat of steel from Table 1? Find the percent error for your calculated specific heat relative to this accepted value.

3. Comment on your percent error. How could you improve the experiment to reduce this error?

4. Does the air inside the calorimeter also gain heat? Why do we exclude this from our calculation?

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Experiment 1: Active Atoms

Questions

1. What was the difference in the spread of the dye between the two glasses?

2. What does this tell you about the movement of the molecules of the warm water versus the cold water?

Experiment 2: Barometric Pressure

Questions

1. How does your barometer allow you to measure changes in atmospheric pressure?

2. In what direction did the arrow point for high pressure? For low pressure? Why?

3. How did the volume of the gas in the container change as the pressure outside increased and decreased? What does this tell you about the relationship between pressure and volume of a gas?

4. Explain how the barometer pictured in Figure 6 could measure changes in atmospheric pressure.

Questions

1. How did you decrease the air pressure in the syringe? What happened to the marshmallow under these conditions?

2. What can you conclude from this experiment about the composition of marshmallows?

3.What would happen to a marshmallow if you put it on the moon (where there is very little atmosphere and thus very low pressure)? What would happen to a marshmallow on Jupiter (which has a very dense atmosphere)?

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Experiment 1: Static Materials

Questions

1. What happens when you bring the charged strip near the paper pieces? Why does this happen?

2. What happened when you brought two vinyl strips near each other? Draw a rough diagram depicting the direction of electric field lines between the two surfaces.

3. What happened when you brought the charged aluminum near the charged vinyl? Draw another diagram noting the direction of the electric field lines between these two surfaces.

4. Do you know which of these materials picks up positive charge and which picks up negative charge? How might it be possible to determine this?

5. What happened when you brought the charged rod near the metal surface? Explain what is happening in terms of free electrons.

Experiment 2: Static Balloons

Questions

1. What types of objects did the balloon stick to best? What can you conclude about the way charges in these objects react to the balloon’s charge?

2. Explain why the balloons either attracted or repelled each other in step 5. What happens when you put your hand in between them?

3. Your hand is a neutral object. Why does this happen if your hand does not carry any net charge (Hint: think about charge by induction)?

Experiment 3: Simple Electroscope

Questions

1. What happens to the strips of aluminum when you bring a charged object near them?

2.What can you say about the charge in the strips—are they like or unlike? How do you know

3.Is your charged electrode like or unlike the charged rod? Why?

4.Does it matter which charge—positive or negative—is on the object you are testing?

5.Is this an example of charge by induction or conduction?

Lab 4: Pith Ball Electroscope

Questions

1. What happened when you brought the charged vinyl near the electroscope?

2. What did you notice when you brought the aluminum strip near the pith ball that was charged by the vinyl?

3. Use Coulomb’s law to explain why the electroscope does not seem to be affected by the charged material at a distance of about 10 cm, but reacts significantly at a distance of 3 cm (distances are approximate).

4. How could you design an experiment to measure the Coulomb force between the charged material and the electroscope by measuring the angular acceleration of the electroscope? Assume you have measured the radius of the rotating electroscope, R, and the distance between the charged material and the pith ball, r.

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## PHYS 320 Lab 23 Properties of Waves | DeVry Online Help

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Questions

1. What happened when the transverse waves reached your partner’s end? Did the returning wave stay on the same side as the one you sent? Explain why you think this happens.

2. Did the waves seem to go any faster or slower when you tried a variety of amplitudes? Explain why or why not this agrees with the equation for a transverse wave’s velocity.

3. What did you notice about the speed of the longitudinal waves compared to the transverse waves? Why do you think this is?

4. Explain what happened when you and your partner both sent waves on the same side in Procedure 2. What kind of interference took place?

5. What happened when waves on opposite sides passed each other?

6. How did shortening the length of the spring affect the resonant frequencies?

7. Using this knowledge, how do you think woodwind instruments create higher and lower tones? What do you think changes inside the instrument?

Experiment 2: Doppler Effect

Questions

1. Did the waves in front of the moving source appear closer together?

2. What can you conclude about the effect of a moving source on the velocity of the waves in a medium?

3. How does the Doppler Effect help explain why a car’s engine sounds different as the car approaches you compared with after it passes?

4. The Doppler Effect is present in light waves as well. As you will learn in Lab 25, red light has a slower frequency than blue light. What can you speculate about the motion of a distant star that appears “red-shifted” to astrophysicists?

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Experiment 1: Can Crusher

Questions

1. According to Charles’ Law, what should happen to the volume of the gas in the can when you decrease the temperature?

2. According to Gay-Lussac’s law, what should happen to the pressure of the gas in the can as you decrease the temperature?

3. Knowing these two principles together, describe the pressure inside the can compared to the outside air after you placed it in the ice water.

4. What force caused the can to crush?

5. Why was it important for you to invert the can as you placed it in the ice water? (Hint: think about what would happen differently if the gas was allowed to escape the can, like the steam you saw in step 3.)

Experiment 2: Charles’s Law Experiment

Questions

1. What happened to the volume of gas when the syringe was submerged in each water bath? Using the concepts discussed above, describe why this occurs, keeping in mind the definition of temperature.

2. Using a ruler, draw a straight line of best fit through your data points, extrapolating the line until it intersects the (negative) x-axis. Why can you assume a straight line, i.e., a linear relationship?

3. At what temperature does your line intersect the x-axis? What volume corresponds to this temperature?

4.Do you think it would be possible to cool a real gas down to zero volume? What do you think would happen first?

5. Is your measurement of absolute zero close to the actual value (-273 °C)? How might you change the experiment to get closer to the actual value?

6. When does the air in the syringe do work? When is work being done on the air inside?

Experiment 3: Entropy Simulation

Questions

1. How did the arrangement of pennies change after each shake? Did you get different results based on how many pennies were in the box? Did you ever end with an equal arrangement of heads and tails?

2.After starting with an “ordered” set in step 4, how likely do you think it is to arrive back in a state of “order” after shaking the box numerous times (i.e., end with all heads or all tails)? How do you think this compares to the probability of landing on all heads or tails with only two or four pennies

3.How does this help demonstrate the property of irreversibility in thermal processes (think of the pennies as gas particles in a chamber)?

4.How does this experiment demonstrate a natural progression from an ordered system to a disordered system?

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## PHYS 320 Lab 17 Change of Phase | DeVry Online Help

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Experiment 1: Freezing and Melting

1.How does the addition of salt affect the equilibrium temperature of the ice water mixture?

2.Was there any difference in the amount of condensation that collected on the outside of each cup? Describe why this occurs, and what it suggests about the temperature of each mixture.

3.Compare the temperatures of the two mixtures over the duration they were in the freezer. Is this what you expect? HINT: what is the coldest temperature either mixture can reach given the freezer temperature?

4.Did either cup completely freeze after 30 minutes? How does the addition of salt appear to affect the freezing point of water?

5.In order to freeze an ice cream mixture, its temperature must be brought below approximately -3°C. Explain how surrounding the ice cream in salty ice water brine helps it reach this temperature.

6.Based on what you have observed, explain why it is helpful to spread salt on icy roads and sidewalks in the winter.

Experiment 2: Clouds in a Bottle

Questions

1. Did anything happen when you squeezed the bottle the first time?

2. What happened when you squeezed the bottle after dropping the match in?

3. Explain how the smoke helped the water vapor condense.

4. Clouds are the most visible when the tiny condensed water molecules are densely packed, making a reflective layer that appears white. What would you have to change in this experiment to make your cloud more visible? Hint: how is the density of a gas affected by temperature and pressure?

5. What changes to the air in the bottle allowed condensation to take place?

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