PHYSICS
102
PRE
AND POST QUESTIONS
LAB
HANDOUT
Experiment 17
TEMPERATURE COEFFICIENT of
LINEAR EXPANSION
PreQuestions:
1). Calculate the final length of a bridge given the following data:
When the temperature changes from -20° F to 70° F, the bridge expands 1 meter. The coefficient of linear expansion for steel is 12 x 10-6 per degree Celsius.
2). Name the quantities which are needed in addition to the change in length of the rod in order to calculate the coefficient of linear expansion. Indicate how they are measured. What is the coefficient dependent on?
PostQuestions:
1). Using the measured values of the aluminum rod determine the change in volume it experiences in this experiment. What would the final volume of the aluminum rod be?
2). A glass graduated cylinder has a volume of 250 milliliters at 0° C if the temperature is increased to 45° C will its volume increase or decrease? Calculate the change.
Experiment 18
CALORIMETRY
PreQuestions:
1). Write the equation used to determine the specific heat of copper in terms of the appropriate masses, temperature changes and specific heats (define all quantities). State in one sentence the basic principle of physics expressed by this equation.
2). How much heat is absorbed by 100 grams of water going from 0° C to 30° C if the water starts off as liquid at 0° C. How much heat is absorbed if the water starts off as ice at 0° C?
PostQuestions:
1). A careless student splashes some water outside of the calorimeter cup when he drops the ice cubes in. How would this alone affect the calculated latent heat of fusion of ice? Explain your answer.
2). A piece of ice with a mass of 30 grams at 0° C is added to 100 ml of water at 20° C. Assuming no loss of heat to the surroundings, what is the situation when equilibrium is reached?
Experiment 13
Simple
Harmonic Motion
PreQuestions:
1) In the case of a suspended spring loaded with a particular mass M describe, using Physics terms, what simple harmonic motion is.
2) How do the mass, the spring constant, and the amplitude of the spring described in the experiment affect its period?
PostQuestions:
1) The amplitude of a simple harmonic oscillator is doubled. What happens to: (a) the period, (b) the total energy, (c) the maximum velocity of the mass?
2) Is the acceleration of a simple harmonic oscillator ever zero? If so, where?
Experiment 14
VIBRATING STRING - MELDE'S
EXPERIMENT
PreQuestions:
1). Define the terms:
(a) resonance, (b) standing wave, (c) node, (d) anti node, and (e) constructive interference.
2). A string exhibits standing waves with 4 anti-nodes when a mass of 200 grams is hanging over the pulley (similar to figure 1). What mass will produce a standing wave pattern with 6 anti-nodes?
PostQuestions:
1). As mass is added to the mass holder an elongation or stretching of the string itself may occur. How does this affect the results of the experiment?
2). If you were to use a string which had 4 times the mass of the string used in the experiment, how much tension would have to be applied in order for it to have a standing wave of 3 1/2 wavelengths long? Use values for other parameters from your data.
Experiment 15
THE VELOCITY OF SOUND
PreQuestions:
For the following Pre-Qustions:
velocity of sound at room temperature is approximately 343 m/sec
1). If the frequency is variable and the length of the closed (at both ends) tube is fixed at 45 cm, sketch the plastic tube showing the positions of the nodes and anti-nodes for the three lowest resonant frequencies.
2). If the frequency is held constant at 1350 Hz and the length of the closed (at both ends) tube is increased from zero, sketch the tube showing this expansion of length and the positions of the nodes and anti nodes for the first three resonances.
PostQuestions:
1). A tube, open at one end and closed at the other, is 1 meter long. Calculate the three lowest frequencies for sound which could produce resonance in the tube. Use 343 meters/sec for the speed of sound.
2). Calculate the velocity of sound at -30° F if the velocity at 0° C is taken to be 331.3 m/sec in air.
Experiment 19
EQUIPOTENTIAL PLOTTING AND
THE ELECTRIC FIELD
PreQuestions:
1). How are electric field lines and equipotential lines oriented relative to each other? Directions of fields are indicated on field lines. Why are there no directions indicated on equipotential lines?
2). How are equipotentials determined experimentally?
Post Questions:
1). If the electric potential is constant throughout a region of space, what can you say about the electric field in that region?
2). A conducting disk (short cylinder, so draw a circle to represent it) is placed in the middle of a uniform electric field causing the field to change. Sketch the new force lines and the potential lines both inside and outside the disk.
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Experiment 20
CAPACITANCE
PreQuestions:
1). If the resistance in a capacitor circuit is increased, would the discharging time of the capacitor increase or decrease? Explain.
2. A charged capacitor with a 10 volt potential difference between the plates and a resistance of 2000 W are connected in series (i.e. they form an RC circuit). In 2 milliseconds (2 x 10-3 seconds) the current in the circuit degrades to a value of 0.37 of its initial value. What is the capacitance in micro-Farads?
PostQuestions:
1). What is the general equation for the voltage across a capacitor after a time of two time constants when charging from zero voltage?
2). Capacitor #1 has a dielectric of hard rubber between its parallel plates and capacitor #2 has a dielectric of mica between its parallel plates (all plates are equal in size). Both were each hooked up to a D.C. source of 15 volts and it was found that, after a long time, both exhibited to have the same amount of charge on them. For this to occur what is the ratio of the dielectric thickness of capacitor #1 compared to that of capacitor #2? (Use your text book to find constants associated with the two materials).
Experiment 21
D.C. CIRCUITS
PreQuestions:
1). When resistors are connected in parallel in a circuit, what are the relationships between the voltage drops across the resistors and the currents through the resistors?
2). What is meant by the equivalent external resistance of a circuit? Give a numerical example of a circuit with both series and parallel resistors.
PostQuestions:
1). Which resistor had the dominant effect on the series network? In the parallel network?
Explain why in both cases.
2). To reduce the brightness of a light bulb connected to a constant voltage source, should an auxiliary resistance be connected in series or parallel? Explain.