Find the value of source current (I) from the circuit as shown belowa)...
Concept:
Wheatstone Bridge:
- The Wheatstone Bridge has four resistors R1, R2, R3, and R4.
- A Voltage source is connected across one pair of diagonally opposite points A and C. This is called the battery arm.
- Between the other two vertices, B and D, a galvanometer G is connected. This is called the Galvanometer arm.
- For the sake of simplicity, let us assume that the cell has no internal resistance.
Balanced Bridge:
- The resistors are arranged in such a manner that the current through the galvanometer is zero, i.e. Ig = 0.
- The bridge is said to be balanced when deflection in the galvanometer is zero i.e. no current flows through the galvanometer or in other words VB = VD.
- Under the balanced condition,
- The above equation relates the four resistors is called the balance condition of the Wheatstone Bridge for which the galvanometer will show zero or null deflection.
Explanation:
According to the question given below:

- In the above figure, there are two sets of Balanced Wheatstone bridges.
- We know the condition for a balanced Wheatstone bridge is
- The condition holds true for both the equations mentioned above, therefore, the current in the 2 Ω and 3 Ω is zero.
- We can replace 2 Ω and 3 Ω from the circuit with an open circuit.
- The resistances of the top horizontal line are in series (Ignoring the 2 Ω branch, since no current passes through it).
⇒ Rtop = 2 Ω + 2 Ω = 4 Ω
- The resistances of the middle horizontal line are in series (Ignoring the 3 Ω resistance branch, since no current passes through it).
⇒ Rmidddle = 3 Ω + 3 Ω = 6Ω
- The resistances in the bottom horizontal line are in series.
⇒ Rbottom = 6 Ω + 6 Ω = 12 Ω
- The net resistance is (considering Rtop, Rmiddle, and Rbottom).
- The current through the battery (I) could be obtained by Ohm's Law,
View all questions of this testFind the value of source current (I) from the circuit as shown belowa)...
Concept:
Wheatstone Bridge:
- The Wheatstone Bridge has four resistors R1, R2, R3, and R4.
- A Voltage source is connected across one pair of diagonally opposite points A and C. This is called the battery arm.
- Between the other two vertices, B and D, a galvanometer G is connected. This is called the Galvanometer arm.
- For the sake of simplicity, let us assume that the cell has no internal resistance.
Balanced Bridge:
- The resistors are arranged in such a manner that the current through the galvanometer is zero, i.e. Ig = 0.
- The bridge is said to be balanced when deflection in the galvanometer is zero i.e. no current flows through the galvanometer or in other words VB = VD.
- Under the balanced condition,
- The above equation relates the four resistors is called the balance condition of the Wheatstone Bridge for which the galvanometer will show zero or null deflection.
Explanation:
According to the question given below:

- In the above figure, there are two sets of Balanced Wheatstone bridges.
- We know the condition for a balanced Wheatstone bridge is
- The condition holds true for both the equations mentioned above, therefore, the current in the 2 Ω and 3 Ω is zero.
- We can replace 2 Ω and 3 Ω from the circuit with an open circuit.
- The resistances of the top horizontal line are in series (Ignoring the 2 Ω branch, since no current passes through it).
⇒ Rtop = 2 Ω + 2 Ω = 4 Ω
- The resistances of the middle horizontal line are in series (Ignoring the 3 Ω resistance branch, since no current passes through it).
⇒ Rmidddle = 3 Ω + 3 Ω = 6Ω
- The resistances in the bottom horizontal line are in series.
⇒ Rbottom = 6 Ω + 6 Ω = 12 Ω
- The net resistance is (considering Rtop, Rmiddle, and Rbottom).
- The current through the battery (I) could be obtained by Ohm's Law,