1. In working with a Wheatstone bridge one student choose the value for R_1 so t
ID: 1771707 • Letter: 1
Question
1. In working with a Wheatstone bridge one student choose the value for R_1 so that the bridge is balanced at L_1=48.5cm and L_2=51.5cm. If each measurment has an uncertanity of +Or - 0.05 cm. What would be the minimum value for the uncertanity in the calculation of R_x?
2. A record studemt working with a wheatstone bridge chose a value for R1 such that the balance point is L1= 8.0 cm and L2=92.0 cm. If each vaue for L has an uncertainty of +/-0.05 cm, what is the minimum value for the uncertainty in Rx that could be expected?
3. Based on the answer to question 1 and 2 where should the balance point be made to get the highest precision in the value for Rx?
4. Does the uncertainty (standard devieation) in your value for Rx for spool B alone account for how far your resistivity deviates fromt the standard value of the resistvity of the copper wire used (2.18*10^-8 Ohm-meter)?
Explanation / Answer
1)
Rx = (L2/L1)R1
=> Rx = (51.5 / 48.5)R1
=> Rx = 1.062*R1 ..............(1)
(Rx/Rx) = (L2/L2) + (L1/L1) + (R1/R1)
=> (Rx/Rx) = [+/-(0.05/51.5)] + [+/-(0.05/48.5)] + 0
minimum value will occur when L2 and L1 are of oppsite sign
=> (Rx/Rx)min = +/- 0.00006
Substituting (1) in the above equation,
=> (Rx)min = 0.000064*R1
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