====== Non-linear resistors ======

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

{{drawio>lab_electrical_engineering:1_resistors:Fig-6_Linear-resistors_V1.svg}}\\
<imgcaption Fig-6_Linear-resistors_V1 | Characteristic of a linear resistor> </imgcaption>
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For non-linear resistors, there is no proportionality between current and voltage. The characteristic of such a resistor is shown in <imgref Fig-7_Nonlinear-resistors_V1>. For these resistors, one distinguishes between static resistance $R$ and dynamic (or differential) resistance $r$.

The static resistance is determined for a specific operating point: at a given voltage, the current is read from the characteristic. The calculation is carried out according to Ohm's law:

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

The dynamic 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 of a non-linear resistor> </imgcaption>

An incandescent lamp is investigated as an example of a non-linear resistor. Build the measurement 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 | Measurement circuit for incandescent lamp> </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 | Measured values for the incandescent-lamp characteristic> </tabcaption>

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Plot the characteristic $I = f(U)$.
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Calculate the static resistance $R$ at the operating point $U = 7.0 ~{\rm V}$.
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Calculate the dynamic resistance $r$ at the operating point $U = 7.0 ~{\rm V}$.
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Compare the values with those from the direct resistance measurement (<tabref Table-1_V2>).
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