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Archive for Laboratories

Laboratory #8 – DC Circuits

Posted by: | April 26, 2010 | 1 Comment |

DC Circuits

The lab uses two different light bulbs (let the spherical bulbs be type A and the “elongated” bulbs type B).  You will need 2 A’s and a B.  The energy source is two D batteries in series.

A.            Resistances of the Light Bulbs

1.            How must a voltmeter and ammeter be connected in a circuit?

2.            What has more resistance, a 60-watt or 100-watt light bulb?

3.            Apply Ohm’s law to determine the resistances of your A and B bulbs and determine the power consumed by each.  Noticing which burns brighter, is this consistent with what we have discussed?

Initial Sign-off __________

B.            Light Bulbs in Series

The goal is to determine whether the input voltage equals the sum of the voltages in a loop.

1.         Connect two A’s in series with the batteries.  Measure the output voltage across the batteries and that across each light bulb.  Is what you measured consistent with what you know/expect about series circuits?  Explain.  Also explain any inconsistencies with theory.

2.         If a single A bulb is connected to the batteries, how does its brightness compare with that of 2 in series?  Explain.

3.         With two A’s in series, measure the current.  Is Ohm’s law satisfied (recall that you have determined the resistances of the bulbs)?  Explain any inconsistencies.

4.         Connect an A and a B in series with the batteries and explain what you see.  Measure the output voltage of the batteries and voltage across each bulb.  What is the power consumed by each?  How does this compare with the powers you determined in A(3)?

Initial Sign-off __________

C.            Light Bulbs in Parallel

The goal is to determine whether the total current equals the sum of the currents in the branches.

1.         Connect an A and a B in parallel with the batteries.  Measure the output voltage of the batteries and the voltage across each bulb.  Is what you measured consistent with what you know/expect about parallel circuits?  Explain.  Also explain any inconsistencies with theory.

2.         If a single A bulb is connected to the batteries, how does its brightness compare with an A and a B in parallel?  Try it by connecting an A and then “switching” on a B.  Explain why what you notice is to be expected.

3.            With an A and a B in parallel,

a)            Measure the current through each bulb and the voltage across each.

b)            What is the total current (add the currents from the two loops together) and battery output voltage;

c)            Using the resistances determined in A(1) of the two bulbs, use Ohm’s law to calculate what the total current and current through each bulb “should be” in parallel, and compare this to what was measured in parts (a) and (b).  Explain any differences.

Initial Sign-off __________

under: Laboratories

Laboratory #7 – Pendulum

Posted by: | March 22, 2010 | No Comment |

The Pendulum

The theoretical equation T = 2π sqroot (L/g) describes how the period T of a pendulum (the round trip time) depends on its length L and the acceleration due to gravity g.

1. The theoretical equation is an approximation, as all derivations rely on various assumptions.  Determine experimentally whether T depends on

a. the initial angle or amplitude;

b. the mass of the bob.

Explain clearly what you did.

2. Verify that the above equation has consistent units.  L is measured from where the string is clamped to the center of the “bob”.

3. For each of at least 10 different lengths, using about the same initial (small) angle, carefully measure T with a stopwatch.  Why should you time at least 10 consecutive periods (and then divide by the number you timed) instead of measuring a single period 10 times?

4. Use the appropriate regression to find an experimental relationship between T and L.  Is your result consistent with the theoretical equation? Explain.

5. Assuming that you answered “yes” to the question in (3), use the result of (3) and the theoretical equation to calculate g and a % error.  Explain clearly what you did.  Do NOT simply plug various values of T and L into the theoretical equation and average the g’s.

6. Explain the sixth panel in the cartoon on your handout.  Better yet, apply it to your data and see what happens…

Picture 1

under: Laboratories

Laboratory #6 – Torque

Posted by: | February 17, 2010 | No Comment |

Torque

under: Laboratories

Laboratory #5 – Conservation of Energy

Posted by: | January 6, 2010 | No Comment |

Conservation of Energy

Materials:

Metal Slide, Plastic Ruler, Marble, Meter Stick

Procedure:

Place the marble at the top of the ruler and release it.  Set up the slide so that the marble is allowed to leave the ruler moving essentially horizontally and able to land on the floor.  Ignore the effects of angular momentum.

Analysis:

-What is the speed of the marble just before leaving the ruler?

-What is the speed of the marble just before it hits the ground?

-Thinking about projectiles (Chapter 4), calculate the range of the marble.

-Measure the range and compare that value to the calculated value (using percent error).

Conclude about your findings.  Please be specific and refer to your results as you do so.  With your conclusion should come an error analysis section.

Due Date: Friday, January 8th

under: Laboratories

Laboratory #4 – Springs

Posted by: | November 23, 2009 | No Comment |

Springs

Theory:

The period (time for a complete round trip) of a mass m oscillating on a spring supported vertically is,

T=2π(m/k)^(1/2)

The Period (T) is equal to two pi (π) times the square root of mass (m) divided by the spring constant (k).  For the springs we will use, F = kx, where F is the stretching (or compressing) force and x is the displacement.

Procedure/Analysis:

1. Verify that the first equation has consistent units.  Do this prior to stating the lab.

2. For each of at least 6 different suspended masses,

a. measure the spring stretch x when at equilibrium (using a meter stick).

b. measure the period (T) of oscillation when displaced slightly from equilibrium and released.  Time several periods (5-10) while the stopwatch is running throughout and divide to find T.  Why is this more accurate than timing one period several times and then averaging the results?

3. Using Excel, graph F vs. x, where F is the weight of the suspended masses, to determine k for the spring.  Clearly explain what you did to find k.

4. Using Excel, graph T vs. m and use the appropriate regression to find an experimental relationship between T and m.

a. Use your results from the graph and the theoretical equation to determine k.

b. Explain what you did and what you found about this relationship.  Do Not simply plug in values for T and m and average.

5. Calculate the % difference between the determinations of k in parts 3 and 4 with that of the know k values.  Which was more accurate? Explain.

A discussion of possible errors should be included in the lab.  As always, a conclusion of the lab should be included.  Answering questions from the spring section need not be repeated in your conclusion, but should in many ways serve as your conclusion.

under: Laboratories, Physics

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