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Electricity, circuits. CIE AS

https://gyazo.com/4486c40dee9ecaf2cb84172831cc0a5e

Help please.
Original post by Jian17


The circuit is known as a Wheatstone Bridge. It is formed by two sets of voltage dividers in parallel.

Null current requires the p.d. across the ammeter to be zero. That in turn requires the p.d. at both mid-divider junctions to be at exactly the same p.d. w.r.t. a common supply node.

It means that the ratio of the resistances in both dividers must be the same.

either:

\frac{R1}{R2} = \frac{R3}{R4}

R1\text{x}R4 = R3\text{x}R2

or

\frac{R2}{R1} = \frac{R4}{R3}

R2\text{x}R3 = R1\text{x}R4

Both expressions are satisfied by answer D.
(edited 5 years ago)

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