====== Resistance measurement ======

Procedure for resistance measurement:
  - Set the measuring device to resistance measurement.
  - Connect the resistor to be measured to the corresponding sockets on the measuring device (the sockets labelled COM and $\Omega$).
  - Read the measured value.

There are different types of resistance measurement:
  * **direct** resistance measurement
  * **indirect** resistance measurement

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=== Direct resistance measurement ===
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Determine the nominal and measured values of the resistance for $R_{\rm 1}$ (brown, green, orange), $R_{\rm 2}$ (yellow, violet, red), $R_{\rm 3}$ (red, violet, red), and the incandescent lamp $R_{\rm L}$. Also measure the approximate resistance $R_{\rm K}$ of your body from your right hand to your left hand.

{{drawio>lab_electrical_engineering:1_resistors:Table-1_V2.svg}}
<tabcaption Table-1_V2 | Direct resistance measurement> </tabcaption>
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How do you explain the deviation between $R_{\rm L,nominal}$ and $R_{\rm L,meas}$?
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What consequences can $R_{\rm K}$ have?
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Now determine the series and parallel combinations of resistors $R_{\rm 1}$, $R_{\rm 2}$ and $R_{\rm 3}$. \\
State the formulae used: \\

$R_{\rm series} = R_{\rm a} + R_{\rm b}$ \\
$R_{\rm parallel} = R_{\rm a} \parallel R_{\rm b} = \frac{R_{\rm a} \cdot R_{\rm b}}{R_{\rm a} + R_{\rm b}}$

{{drawio>lab_electrical_engineering:1_resistors:Table-2_V1-Serial+parallel.svg}}
<tabcaption Table-2_V1 | Series and parallel combinations> </tabcaption>
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=== Indirect resistance measurement ===
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Resistance can also be determined by measuring current and voltage.

**Ohm's law:** In an electrical circuit, the current increases with increasing voltage and decreases with increasing resistance. \\
$ I = \frac{U}{R} $

Build the measurement circuit shown in <imgref Fig-1_V1> for each of the three resistors and set the voltage on the power supply to $12 ~{\rm V}$.

{{drawio>lab_electrical_engineering:1_resistors:Fig-1_V1-indirect-measurement.svg}}
<imgcaption Fig-1_V1 | Indirect resistance measurement> </imgcaption>
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Measure $U_{\rm n}$ and $I_{\rm n}$. Calculate $R_{\rm n}$ from these values.

{{drawio>lab_electrical_engineering:1_resistors:Table-3_V1-indirect-measurement.svg}}
<tabcaption Table-3_V1 | Indirect resistance measurement> </tabcaption>