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Question: Answered & Verified by Expert
In a certain region static electric and magnetic fields exist. The magnetic field is given by B=B0i^+2j^-4k^. If a test charge moving with a velocity v=v03i^-j^+2k^ experiences no force in that region, then the electric field in the region, in SI units, is:
PhysicsMagnetic Effects of CurrentJEE MainJEE Main 2017 (08 Apr Online)
Options:
  • A E= -v0 B0i^+j^+7k^
  • B E= -υ0 B03i^-2j^-4k^
  • C E= v0 B014j^+7k^
  • D E=-v0 B014j^+7k^
Solution:
1397 Upvotes Verified Answer
The correct answer is: E=-v0 B014j^+7k^
The total force experienced by test charge is Fe+ Fm=0.

Fe=-Fm

Fe=q0v0B0V×B

Fe=-q0 v0B03i^- j^+2k^×i^+2j^-4k^

Fe= -qv0B0 (14j^ +7k^)

The electric field produced by the test charge is    E= feq= -v0B0 ( 14j^+7k^)

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