In the shown circuit, ammeter I reads 10 mA and the voltmeter reads 3 V. What will identical ammeter II read (in mA, nearest integer)? Battery emf is 4 V; the two central resistors are each 100 Ω. Treat meters as non-ideal and battery resistance as negligible. [See Image.]
Physics · Mixed Chapter
JEE Main Practice

Question

In the shown circuit, ammeter I reads 10 mA and the voltmeter reads 3 V. What will identical ammeter II read (in mA, nearest integer)? Battery emf is 4 V; the two central resistors are each 100 Ω. Treat meters as non-ideal and battery resistance as negligible. [See Image.]

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1 — Battery fixes 4 V between top and bottom rails. Voltmeter reads 3 V between its top node and ground. Thus ammeter I drops 4−3 = 1 V. Step 2 — Ammeter I reads 10 mA, so each ammeter has resistance r = 1/0.010 = 100 Ω. Step 3 — If V is the central junction potential, KCL gives (V−4)/100 + V/100 + (V−3)/100 = 0, so V = 7/3 V. Step 4 — Ammeter II carries magnitude |(7/3−3)/100| = 1/150 A = 6.667 mA. Rounded to nearest integer: 7 mA.