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A \'Wheatstone bridge\' is a device that measures resistances. In the circuit sh

ID: 2280281 • Letter: A

Question

A 'Wheatstone bridge' is a device that measures resistances. In the circuit shown in the diagram below, R is an unknown resistance. The resistances R1, R2, and R3 are variable. A galvanometer, G, can be

used to determine when the potential difference between b and c is zero, given that the battery is connected between a and d. The variable resistances are adjusted until there is no current in the galvanometer when the switch, S, is closed. Suppose that the galvanometer reads zero for a particular circuit, determine an expression for R in terms of R1, R2, and R3. To check your answer, consider the

case when R1 = 26 ?, R2 = 71 ?, and R3 = 14 ?. What is the value of the unknown resistor R when the galvanometer reads zero as the switch is closed?

A 'Wheatstone bridge' is a device that measures resistances. In the circuit shown in the diagram below, R is an unknown resistance. The resistances R1, R2, and R3 are variable. A galvanometer, G, can be used to determine when the potential difference between b and c is zero, given that the battery is connected between a and d. The variable resistances are adjusted until there is no current in the galvanometer when the switch, S, is closed. Suppose that the galvanometer reads zero for a particular circuit, determine an expression for R in terms of R1, R2, and R3. To check your answer, consider the case when R1 = 26 ?, R2 = 71 ?, and R3 = 14 ?. What is the value of the unknown resistor R when the galvanometer reads zero as the switch is closed?

Explanation / Answer

R1 = 26 ?, R2 = 71 ?, and R3 = 14 ?


R / R2 = R1 / R3

R = 71*26/14

=131.86 Ohm

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