A point charge q=1μC is located at a distance 2 cm from one end of a thin insulating wire of length 10 cm having a charge Q=24μC, distributed uniformly along its length, as shown in figure. Force between q and wire is ____ N. (Use 4πϵ01=9×109N.m2/C2)
Answer: 90
Solution
The wire carries uniform linear charge density λ=LQ=0.124×10−6C/m. An element at distance x from the point charge exerts dF=x2kqλdx, and integrating across the wire, whose near and far ends are 0.02 m and 0.12 m from q, F=kqλ∫0.020.12x2dx=kqλ(0.021−0.121). Substituting, F=9×109×10−6×0.124×10−6×3125=90 N. The force between the charge and the wire is 90 N.
JEE Main · 2026 · 24 Jan 2026 · Shift 2 · Integer answer