The Thevenin voltage for the thermocouple at 1000 deg. is 42 mV.
Assume that the amplifier is ideal; that is, that the input impedance is infinite.
Hint for P8.19
The resistance of one length of 100 ft is 6.4 ohm. Double it and add the 2.0 ohm of the thermocouple to find the Thevenin resistance of the thermocouple+lead assembly.
Hint for E8.1
The Thevenin generator for the capacitance bridge is VTH = 50 mV and ZTH = -j20k.
Hint for E8.2
Rationalize the denominator of Eq. 8.1.