A circuit can be used to measure the resistance of a platinum resistance thermometer (PRT). AB is a uniform resistance wire of length 1.0mandCisa sliding contact on this wire. A standard resistor R is included in the circuit. The position of C is adjusted until the voltmeter V reads zero.

Question

(i) By applying Kirchhoff’s laws to loops ADCA and BCDB, deduce an expression for the resistance of the PRT in terms of l1,land the value of the standard resistor.

(ii) The PRT consists of 9.0 m of wire of diameter 8.0×10−2 mm. The voltmeter reads 0 V when l1 =0 .44m. If the standard resistor, R, has a resistance of 224Ω, what is the resistivity of platinum? Show that you have checked that the value for the resistivity and its unit are sensible

Answer 1

I'm not sure how tutors here can be of much help without the diagram for this one.

Though I suppose you're supposed to equate the potential drop across the circuit with that of the PRT, since the Voltmeter reads zero.