Question

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=

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Answer 2

E =

p.d. V =$\frac { \lambda } { 2 \pi \varepsilon _ { 0 } }$ln E = B varies with r B = B and E are perpendicular to each other

\ q u B = qE

(If particle travel undeviated) u = $\frac { E } { B }$ = $\frac { 2 \pi \mathrm { V } } { \mu _ { 0 } \operatorname { I } \ln \left( \frac { \mathrm { a } } { \mathrm { b } } \right) }$