Measurement of unknown frequency using Wien’s bridge.

Experiment No.: 10

Aim of the Experiment: –

Measurement of unknown capacitance using Wien’s bridge.

Apparatus Required: –

Sl. No.	Name	Specification	Quantity
1	Wien’s Bridge kit		1 no.
2	Head phones		1 no.
3	Patch cord	PVC insulated copper	As per required

Circuit Diagram: –

Theory: –

The wien bridge is generally used to determine unknown frequency of supply. The bridge has a series R-C combination in one arm and a parallel combination in the adjoining arm.

Procedures: –

1. Connect the AC supply of unknown frequency with the terminals marked supply and head phone with the terminal marked detector.
2. Set the resistance dial R₄ at 200 Ω and R₃ at 100 Ω.
3. Now adjust the decade resistance dial R₁=R₂ to minimize the sound in the head phone.
4. Note the value R₁=R₂, and C.
5. Calculate the value of unknown frequency using above formula.
6. Repeat the experiment at another value of R₃ and R₄.

Note: The R₄ resistance should be always taken two times of R₃ resistance to balance the bridge. Else the bridge will never achieve balance state.

Observation Table: –

Sl. No.	Selector frequency	Sl. No.	R3	R4	R1=R2=R	f=(1/2πRC)	Average f
1	Unknown frequency 1	1
		2
		3
		4
2	Unknown frequency 2	1
		2
		3
		4
3	Unknown frequency 3	1
		2
		3
		4
4	Unknown frequency 4	1
		2
		3
		4

Conclusion: –

To be written by student.