NTA Abhyas JEE Main2020PhysicsElectrostaticsPractice
Two long concentric cylindrical conductors of radii a and b b < a are maintained at a potential difference V and carry equal and opposite currents I . An electron with a particular velocity u parallel to the axis will travel undeviated in the evacuated region between the conductors. Then u =
Options
- A4 π V μ 0 I   ln b a
- B2 π V μ 0 I   ln a b
- C2 π V μ 0 I   ln b a
- D8 π V μ 0 I   ln a b
Correct answer
B. 2 π V μ 0 I   ln a b
Step-by-step solution
E = λ 2 π ε 0 r p.d. V = λ 2 π ε 0 ln a b E = V r ln a b B varies with r B = μ 0 I 2 π r B and E are perpendicular to each other ∴ q u B = q E (If particle travel undeviated) u = E B = 2 π V μ 0 I ln a b