==== Nonlinear resistors ====
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All resistors examined so far are linear resistors, for which the characteristic curve $I=f(U)$ is a straight line, s. <imgref Fig-6_Linear-resistors_V1>.
The resistance value of a linear resistor is independent of the current $I$ flowing through it or the applied voltage $U$.	

{{drawio>lab_electrical_engineering:1_resistors:Fig-6_Linear-resistors_V1.svg}}\\
<imgcaption Fig-6_Linear-resistors_V1 | Characteristic curve of a linear resistor> </imgcaption>
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With nonlinear resistors, there is no proportionality between current and voltage. The characteristic curve of such a resistor is shown in <imgref Fig-7_Nonlinear-resistors_V1>. With these resistors, we talk about static resistance ($R$) and dynamic (or differential) resistance ($r$). The static resistance is determined for a specific operating point: at a specific voltage, the current is read from the resistance characteristic curve. \\
The calculation is performed according to Ohm's law:	

$$ R = \frac{U}{I} $$

The differential resistance around the operating point is calculated from the current difference caused by a change in the applied voltage:

$$ r = \frac{\Delta U}{\Delta I} $$

{{drawio>lab_electrical_engineering:1_resistors:Fig-7_Nonlinear-resistors_V1.svg}}\\
<imgcaption Fig-7_Nonlinear-resistors_V1 | Characteristic curve of a nonlinear resistor> </imgcaption>

A light bulb is examined as an example of a nonlinear resistor. Set up the measuring circuit shown in <imgref Fig-8_light-bulb_V1>. \\

{{drawio>lab_electrical_engineering:1_resistors:Fig-8_light-bulb_V1.svg}}\\
<imgcaption Fig-8_light-bulb_V1 | Measuring circuit light bulb> </imgcaption>
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Set the voltage on the power supply to the voltage values from <tabref Table-6_light-bulb_V1>. Measure the corresponding current values and enter them in <tabref Table-6_light-bulb_V1>.

{{drawio>lab_electrical_engineering:1_resistors:Table-6_light-bulb_V1.svg}}\\
<tabcaption Table-6_light-bulb_V1 | Values characteristic curve light bulb> </tabcaption>

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Create the characteristic curve $I = f(U)$, s. <imgref Fig-9_light-bulb-curve_V1>

{{drawio>lab_electrical_engineering:1_resistors:Fig-9_light-bulb-curve_V1.svg}}\\
<imgcaption Fig-9_light-bulb-curve_V1 | Characteristic curve light bulb> </imgcaption>

Calculate the static resistance $R$ at the operating point $U = \rm 7.0 ~V$:
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Calculate the dynamic resistance $r$ at the operating point $U = \rm 7.0 ~V$:
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Compare the values with the values from <tabref Table-1_V2> (direct resistance measurement)