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COMEDK · Physics · 21. Magnetic Effects of Current

Two very long straight parallel wires carry currents \(i\) and \(2 i\) in opposite directions. The distance between the wires is \(r\). At a certain instant of time a point charge \(q\) is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity \(v\) is perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is

  1. A zero
  2. B \(\frac{3 \mu_0}{2 \pi} \frac{i q v}{r}\)
  3. C \(\frac{\mu_0}{\pi} \frac{i q v}{r}\)
  4. D \(\frac{\mu_0}{2 \pi} \frac{i q v}{r}\)
Verified Solution

Answer & Solution

Correct Answer

(A) zero

Step-by-step Solution

Detailed explanation

The magnetic field induction at \(P\) due to currents through both the wires is \(B=\frac{\mu_0}{4 \pi} \frac{2 i}{(r / 2)}+\frac{\mu_0}{4 \pi} \frac{2(2 i)}{(r / 2)}=\frac{\mu_0}{4 \pi} \cdot \frac{12 i}{r}\) acting perpendicular to plane of wire inwards. Now, \(B\) and \(v\)…