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Question: Answered & Verified by Expert
Two infinitely long wires each carrying the same current and pointing in +y direction are placed in the xy- plane, at x=-2 cm and x=1 cm. An electron is fired with speed U from the origin making an angle of +45° from the x - axis. The force on the electron at the instant it is fired is
[ B0 is the magnitude of the field at origin due to the wire at x=1 cm alone].
PhysicsMagnetic Effects of CurrentAP EAMCETAP EAMCET 2022 (04 Jul Shift 1)
Options:
  • A -eUB022i^-j^
  • B -eUB02i^-j^
  • C -eUB02i^-j^
  • D -eUB0i^-j^
Solution:
1230 Upvotes Verified Answer
The correct answer is: -eUB022i^-j^

Magnetic field at origin due to wire at x=1 cm is

B0=μ0i2π0.01

Magnetic field at origin due to wire at x=-2 cm is

B=μ0i2π0.02

Therefore, the net magnetic field at origin will be,

Bnet=μ0i2π0.02=B02 k^

The velocity of the electron is given as v=U2i^+U2j^

The force on the electron will be,

F=ev×B=eU2i^+U2j^×B02 k^F=-eUB022i^-j^

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