number 3 Open the SPST switch U1 to change the contacts to a new R1, . or if the
ID: 1642057 • Letter: N
Question
number 3
Open the SPST switch U1 to change the contacts to a new R1, . or if the switch is absent turn off the P/S. Starting from zero, you will have about six "samples" of voltage and current from your manual "sweep". The Canadian made board has five wire wound resistors of varying lengths and cross sections. We will measure common composition (Cu) resistors number 1, 2, 3, and 4. These wires have definite lengths and diameters as noted on the board. The second board number is American Wire Gauge (AWG) in which a larger number means a smaller diameter wire. Plot the V-I data on graph paper or use a computer spreadsheet program with voltage on the vertical axis. Determine the slopes of the four plots by calculating the Delta V/Delta I (rise/run) ratios. Report attachments: four V-I plot- four slope calculations, one data table with V, I columns for resistors number 1, 2, 3, and 4. Questions: Examine the 4 V-I plots and indicate if they appear to show a linear relationship between V and I. Which of your resistors has the least resistance to the flow of current as shown by the slope of the plots? What is the likely reason that ammeters are connected in series, before or after a circuit component, to measure current? What is the likely reason that voltmeters are connected in parallel, before and after a circuit component, to measure voltage? Describe any influence from AWG or wire length on the slope of your graphs.Explanation / Answer
Solution:
An ammeter is connected in series with the circuit because the purpose of the ammeter is to measure the
current through the circuit. Since the ammeter is a low impedance device, connecting it in parallel with the circuit
would cause a short circuit, damaging the ammeter and the circuit.
There are mainly two majoe reasons:
1) It should be connected in series, so that maximum current can pass through it, for accurate measurement of
current.
2) its resistance is very low, if it is connected in parallel in a circuit, it will by the current, and current can not be
measured accurately.
if you do not connect the ammeter in series you will shunt the load, basically excluding the resistive element of the
circuit.
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