Wheatstone bridge Numerical questions and Solutions – Electrical Measurements
1. The measurement of an unknown resistance R is to be carried out using the Wheatstone bridge. Two students perform an experiment in two ways. The first student takes R2 = 10Ω and R1 = 5Ω. The other student takes R2 = 1000Ω and R1= 500Ω. In the standard arm, both take R = 5Ω. Both find R = (R2/R1)R3 = 10Ω within errors.
- The errors of measurement of the two students are the same.
- Errors of measurement do depend on the accuracy with which R2 and R1 can be measured.
- If the student uses large values of R2 and R1 the currents through the arms will be feeble. This will make the determination of null point accurately more difficult.
- Wheatstone bridge is a very accurate instrument and has no error in measurement.
2. Four arms of a Wheatstone bridge are as follows: AB = 100 Ω, BC = 10 Ω, CD = 4 Ω, DA = 50 Ω. A galvanometer with an internal resistance of 20 Ω is connected between BD, while a battery of 10-V dc is connected between AC. Find the current through the galvanometer.
- 6.24 mA
- 5.18 A
- 5.18 mA
- 51.8 mA
3. Four arms of a Wheatstone bridge are as follows: AB = 100 Ω, BC = 10 Ω, CD = 4 Ω, DA = 50 Ω. A galvanometer with an internal resistance of 20 Ω is connected between BD, while a battery of 10-V dc is connected between AC. Find the value of the
resistance to be put on the arm DA so that the bridge is balanced
- 40 Ω
- 50 Ω
- 20 Ω
- 10 Ω
4. In a Wheatstone’s bridge P = 50 Ω, Q = 100 Ω and R = 20 Ω. If the galvanometer shows zero deflection, determine the value of S.
- 20 Ω
- 40 Ω
- 50 Ω
- 25 Ω
5. The four arms of a Wheatstone bridge are as follows: AB = 100 Ω, BC = 1000 Ω, CD = 4000 Ω, DA = 400 Ω. A galvanometer with an internal resistance of 100 Ω and a sensitivity of 10 mm/μA is connected between AC, while a battery of 4 V dc is connected between BD. Calculate the deflection if the resistance of arm DA is changed from 400 Ω to 401 Ω.
- 20.4 mm
- 204 mm
- 2.04 mm
- 0.204 mm
6. What is the value of x when Wheatstone’s network is balanced?
P = 500 Ω, Q = 800 Ω, R = x + 400, S = 1000 Ω
7. A Wheatstone bridge has P = 3.5 kΩ, Q = 7 kΩ, and galvanometer null is obtained when S = 5.51 kΩ. Determine the resistance measurement range for the bridge if S is adjustable from 1 kΩ to 8 kΩ.
- 500Ω to 400Ω
- 4Ω to 500Ω
- 500Ω t0 4Ω
- 50Ω to 40Ω
8. In Wheatstone’s bridge arrangement PQRS, the ratio arms P and Q are nearly equal. The bridge is balanced when R = 500Ω. On interchanging P and Q, the value of R for balancing is 510Ω. Find the value of S.
9. Four resistances 4Ω, 8Ω, XΩ and 6Ω are connected in a series so as to form Wheatstone’s network. If the network is balanced, find the value of ‘X
10. Resistances in the branches of Wheatstone’s bridge are 30Ω, 60Ω, 15Ω and a series combination of X and 5Ω resistances. If the bridge is balanced then value of unknown resistance X is