A Wheatstone bridge is type of bridge circuit used to make measurements of resistance. The unknown resistance

A Wheatstone bridge is type of €œbridge circuit€ used to make measurements of resistance. The unknown resistance to be measured, Rx, is placed in the circuit with accurately known resistances R1, R2, and R3 (Fig.19-61). One of these, R3, is a variable resistor which is adjusted so that when the switch is closed momentarily, the ammeter (A) shown zero current flow.
(a) Determine Rx in terms of R1, R2, and R3.
(b) If a Wheatstone bridge is €œbalanced€ when R1 = 630Ω, R2 = 972Ω and R3 = 42.6 Ω, what is the value of the unknown resistance?

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AmmeterC R2