In the figure shown, the current in the 10 V battery is close to:
(A)0.71 A from positive to negative terminal
(B)0.42 A from positive to negative terminal
(C)0.21 A from positive to negative terminal✓ Correct
(D)0.36 A from negative to positive terminal
Answer: (C)
Solution
Label the two mesh currents and apply Kirchhoff's voltage law. Around the loop carrying the 20V source, −20+2i1+10(i1+i2)+5i1=0, that is 17i1+10i2=20. Around the loop carrying the 10V source, −10+4i2+10(i1+i2)=0, that is 10i1+14i2=10. Solving the pair gives i2≈−0.21A; the negative sign simply says the current in the 10V battery runs from its positive to its negative terminal, with a magnitude close to 0.21A.
JEE Main · 2020 · 06 Sep 2020 · Shift 2 · Single correct option