Resistance and DC circuits Experiment details
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Resistance and DC circuits
Experiment details
NB. Many measurements in this experiment have uncertainty values associated with them. Please be aware that you might need to use these uncertainties when calculating results in the lab quiz or report using the propagation of error method (see Tutorial 3).
1) Resistance and temperature
It is your birthday and your physics teacher gives you two coils ofwire as a gift, one made from pure aluminum and the other made from pure brass. Since you are a keen physics student, you decide it would be fun to figure out what are the temperature coefficients of resistivity (
) for the two metals. You take your trusty ohmmeter (that measures resistance) and connect the probes to the aluminum coil and begin your measurements. In order to cool the wire coil below room temperature (
0 = 20 °C), you immerse it in a cold water bath and to heat it above room temperature, you blow hot air on it with your mom’s hair dryer. You then repeat the measurements for the brass wire and record all your data in Table 1.
NB. The uncertainty on each temperature measurement is ± 1 °C and each resistance measurement is 2% of the recorded value.
Table 1 - Resistance values ofaluminum and brass wire for different temperatures
|
Temperature (°C) ± 1 °C |
Resistance aluminum (Ω) ± 2% |
Resistance Brass (Ω) ± 2% |
|
10 |
6.25 |
8.60 |
|
15 |
6.38 |
8.71 |
|
20 |
6.51 |
8.81 |
|
25 |
6.60 |
8.91 |
|
30 |
6.72 |
8.99 |
|
35 |
6.85 |
9.08 |
|
40 |
7.03 |
9.14 |
|
50 |
7.24 |
9.33 |
|
60 |
7.51 |
9.58 |
2) Resistance and length
Since you had so much fun measuring the resistance of your coils as a function of temperature, you decide it would be equally fun to measure the resistance as a function of length to try to figure out the resistivity values (
) of aluminum and brass. The wires are cylindrical and you measure the diameter of each type of wire and find 
Al = (1.05 ± 0.05) mm and 
Br = (1.25 ± 0.05) mm. You then cut off various lengths of your wires and measure the resistances of each one and record your data in Table 2.
NB. The uncertainty on each length measurement is ±0.1 m and each resistance measurement is 2% of the recorded value.
Table 2 - Resistance values ofaluminum and brass wire for different lengths
|
Length (m) ± 0.1 m |
Resistance aluminum (Ω) ± 2% |
Resistance brass (Ω) ± 2% |
|
5.0 |
0.15 |
0.26 |
|
10.0 |
0.31 |
0.51 |
|
15.0 |
0.51 |
0.72 |
|
20.0 |
0.66 |
0.95 |
|
25.0 |
0.80 |
1.24 |
|
30.0 |
0.99 |
1.49 |
3) DC Circuits
Using your aluminum and brass wires, you decide to build a few resistors. Using these resistors and a few AA batteries, you construct some interesting circuit combinations to analyse (as shown in Figure 1). Some of the details you might be interested in finding about your circuits are the current that goes through each resistor, the rate at which each battery transfers energy to the circuit, and the rate at which each resistor dissipates electrical energy.
Fig. 1 - Circuit combinations with resistors and batteries
2022-02-26