The following circuit is used as a thermostat. When the temperature rises above a critical value (), the comparator output goes high, indicating overtemperature.

The circuit employs an NTC thermistor () for temperature sensing, with at 25 °C and , assumed constant for all the temperature range.

Determine the temperature (in °C) at which the comparator changes its output value (i.e., ).

In the following circuit the thermistor NTC has at and .

The digital voltmeter (DVM), measuring the output , indicates . Obtain the temperature at the thermistor in °C.

Consider the following circuit in which the thermistor NTC has at and .

Determine the output voltage when the temperature is .

The Wien bridge shown in the figure is used as a null frequency detector when driven by an ac voltage.

Adjusting and , there is a null detection observed when and .

The standard capacitors (fixed-value) are , and .

Determine the detected null frequency.

In order to characterize a capacitor at , both and were adjusted to achieve equilibrium on the Schering bridge shown below. The capacitor to be characterized is modeled by its capacitance value and equivalent series resistance .

Under bridge equilibrium conditions, and . The standard fixed-value components are and .

Determine the dissipation factor (loss tangent, ) of the capacitor to be characterized.

Consider the following Maxwell inductance bridge circuit used to characterize the inductance modeled as the self-inductance and its equivalent series resistance .

By properly adjusting the variable resistor  and the variable self-inductance , the bridge is kept in equilibrium at , i.e. .

Under these circumstances, .

As for the inductor , its equivalent series resistance is .

Estimate the ratio between the unloaded quality factors of the inductors and (without in ), i.e. .

The Schering bridge shown in the figure is used to characterize a capacitor modeled by its value and equivalent series resistance .

Assuming bridge equilibrium conditions, and . The standard fixed-value components are and .

Determine the equivalent series resistance value .

For the Hay bridge shown in the figure, assuming the bridge is in equilibrium, at the frequency of , calculate the series parasitic resistance of the inductor, , considering , , , and .

Consider the following Hay bridge for inductance measurements.

Suppose that and were adjusted ( and ) to achieve bridge equilibrium at , i.e., .

The standard fixed-value components are and .

Determine the value of the inductor, .

For the Maxwell-Wien bridge shown in the figure in equilibrium (null detection between terminals and ) the values of the variable components are and . The fixed-value components are and .

Calculate the self-inductance .