Unformatted text preview: at the end of the experiment to save the batteries. 3.3 Pasco Scientiﬁc PK-9025 conductive paper with point electrodes Point electrodes are the simplest form of a dipole. For this experiment, the point electrodes have been
drawn onto conductive paper with a silver conductive ink pen. The ink has silver particles suspended in
liquid. These silver particles settle on top of each other as the ink dries, which forms a conductive path.
The resistance of the ink is quite low, between 0.03 and 0.05 Ω/cm for a 1 mm wide line. The conductive
paper on which the electrodes are drawn has signiﬁcantly higher resistance (on the order of several 10s of
kΩ/cm). The resistance of the paper allows a current ﬂow, which produces a potential difference between
the electrodes. 3.4 Vernier EKG Sensor The Vernier EKG Sensor measures cardiac electrical potential waveforms . The EKG is a graphic
tracing of the heart’s electrical activity. Any deﬂection measured from the baseline isoelectric line denotes
The EKG trace is a vector sum. The black electrode is the reference point; the voltage offset of
the isoelectric line comes from this electrode. The red electrode is the positive electrode and the green
electrode is the negative electrode. Together, these two electrodes form a "lead". The vector direction of
this lead is from negative to positive. In Lead I conﬁguration (see Section 5), this means that the lead
vector is pointing from right to left. Electrical signal that is traveling in this same direction registers as a
7 positive deﬂection from the isoelectric line. Electrical signal that travels in the direction opposite, left-toright, registers as a negative deﬂection . Any vertical components of the electrical activity cannot be
measured with this lead conﬁguration. 3.5 Vernier Go!Link The Vernier Go!Link adapts the output of the EKG Sensor to USB for easy connection to a computer. 3.6 Vernier’s Logger Lite 1.6.1 software "Logger Lite makes collecting science and math data easier than ever. The simple interface makes
learning intuitive by making science visual." 4 Experiment: Equipotential Map The purpose of this experiment is to gain a basic understanding of potential differences. We will
explore this by making a map of equipotential lines from a dipole conﬁguration of electrodes.
Obtain a piece of conductive paper from your GSI. The conductive paper is marked in centimeters. At
(10,10) and (20,10), there are electrodes drawn on with silver ink. The size of these electrodes is small
enough compared to the distance between them that we can consider this to be a point dipole. Figure 4: "Point" electrode dipole, with three equipotential lines labeled.
Connect each output of the power supply to one of the electrodes on the conductive paper. The banana
cable plugs into the output of the power supply. The ring end connects to the electrode; use the provided
8 thumbtacks to slip over the ring and stab through the electrode into the cork board. Turn the power supply
on and adjust the voltage to read 10V.
Connect the point probes to the DMM. Be sure to use the "COM" and "V" inputs since we will be
measuring voltage. Turn the dial to the V. Test the setup in a few ways:
• Hold both probes to the same thumbtack. The voltage should read zero.
• Hold each probe to one of the elect...
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