Question

What frequency is used to measure bridges?

Answer 1

Max Wien invented the Wien bridge, which is a type of bridge circuit. Four resistors and two capacitors make up the bridge. Bridge circuits were a common way of measuring component values by comparing them to known values at the time the Wien bridge was invented.

Complete answer:
In AC circuits, the Wien's bridge is used to determine the value of an unknown frequency. The bridge detects frequencies between $100Hz$ and $100kHz$ . The bridges' accuracy ranges from $0.1$ to$0.5\%$ . The bridge is also used in a capacitance measurement system, a harmonic distortion analyzer, and an HF frequency oscillator.
Additional Information:-
The Wien's bridge is sensitive to frequency. As a result, obtaining the balance point in it is difficult. There are some harmonics in the input supply voltage, which is not purely sinusoidal. The harmonics of the supply voltage destabilise the bridge's balance. The filter is used in the bridge to solve this problem. The null detector is connected to the filter in series.
A Wien bridge oscillator has become the most popular audio frequency range signal generator circuit due to advantages such as good frequency stability, very low distortion, and ease of tuning. Because this type of oscillator uses an RC feedback network, it is also known as an RC oscillator.

Note:
It's worth noting that the Wien bridge doesn't require equal $R$ and $C$ values. The series ${R_2}-{C_2}$ arm's reactance will be an exact multiple of the shunt ${R_x}-{C_x}$ arm at some frequency. The bridge is balanced if the two ${R_3}$ and ${R_4}$ arms are adjusted to the same ratio.