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Diffstat (limited to 'blackbody.tex')
| -rw-r--r-- | blackbody.tex | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/blackbody.tex b/blackbody.tex index cf4bf56..e99ea18 100644 --- a/blackbody.tex +++ b/blackbody.tex @@ -113,7 +113,16 @@ S[W/m^2]=\frac{S[mV]}{22 [mV/mW]}\cdot 10^{-3}\cdot \frac{1}{4\cdot \end{boxedminipage} % % -\item When the cube has reached thermal equilibrium the ohmmeter will be fluctuating around a constant value. Record the resistance of the thermistor in the cube and determine the approximate value of the temperature using data table in Fig~\ref{tcube}. Use the radiation sensor to measure the radiation emitted from the four surfaces of the cube. Place the sensor so that the posts on its end are in contact with the cube surface (this ensures that the distance of the measurement is the same for all surfaces) and record the sensor reading. Each lab partner should make an independent measurement. +\item When the cube has reached thermal equilibrium the ohmmeter will be + fluctuating around a constant value. Record the resistance of the + thermistor in the cube and determine the approximate value of the + temperature using the data table in Fig~\ref{tcube}. Use the + radiation sensor to measure the radiation emitted from the four + surfaces of the cube. Place the sensor so that the posts on its end + are in contact with the cube surface (this ensures that the + distance of the measurement is the same for all surfaces) and + record the sensor reading. Each lab partner should make an + independent measurement. \item Place the radiation sensor approximately 5~cm from the black surface of the radiation cube and record its reading. Place a piece of glass between the sensor and the cube. Record again. Does window glass effectively block thermal radiation? Try observing the effects of other objects, recording the sensor reading as you go. @@ -188,8 +197,8 @@ Lamp, Power supply. % Resistance of filament (room temperature)=&$\underline{\hskip .7in}$ %\end{tabular} -\item connect a multimeter as voltmeter to the output of the power supply. - {\bf Important:} make sure it in the {\bf voltmeter mode}. +\item Connect a multimeter as voltmeter to the output of the power supply. + {\bf Important:} make sure it is in the {\bf voltmeter mode}. Compare voltage readings provided by the power supply and the multimeter. Which one is the correct one? Think about your measurement uncertainties. @@ -245,7 +254,13 @@ is true for a lamp. \begin{enumerate} \item Set up the equipment as shown in Fig. \ref{bb31}. Tape the meter stick to the table. Place the Stefan-Boltzmann lamp at one end, and the radiation sensor in direct line on the other side. The zero-point of the meter stick should align with the lamp filament (or, should it?). Adjust the height of the radiation sensor so it is equal to the height of the lamp. Align the system so that when you slide the sensor along the meter stick the sensor still aligns with the axis of the lamp. Connect the multimeter (reading millivolts) to the sensor and the lamp to the power supply. \item With the {\bf lamp off}, slide the sensor along the meter stick. Record the reading of the voltmeter at 10 cm intervals. Average these values to determine the ambient level of thermal radiation. You will need to subtract this average value from your measurements with the lamp on. -\item Turn on the power supply to the lamp. Set the voltage to approximately 10 V. {\bf Do not exceed 13 V!} Adjust the distance between the sensor and lamp from 2.5-100 cm and record the sensor reading. \textbf{Before actual experiment think carefully about at what distances you want to take the measurements. Is taking them at constant intervals the optimal approach? At what distances you expect the sensor reading change more rapidly?} +\item Turn on the power supply to the lamp. Set the voltage to + approximately 10 V. {\bf Do not exceed 13 V!} Adjust the distance + between the sensor and lamp from 2.5-100 cm and record the sensor + reading. \textbf{Before the actual experiment think carefully about + at what distances you want to take the measurements. Is taking them + at constant intervals the optimal approach? At what distances you expect + the sensor reading change more rapidly?} \item Make a plot of the corrected radiation measured from the lamp versus the inverse square of the distance from the lamp to the sensor $(1/x^2)$ and do a linear fit to the data. How good is the fit? Is this data linear over the entire range of distances? Comment on any discrepancies. What is the uncertainty on the slope? What intercept do you expect? Comment on these values and their uncertainties? |