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KCET · Physics · Magnetic Effects of Current

Biot-Savart law indicates that an electron moving with a velocity \(\vec{V}\) produces a magnetic field \(\vec{B}\) around it such that

  1. A \(\vec{B}\) is parallel to \(\vec{V}\)
  2. B \(\vec{B}\) is perpendicular to \(\vec{V}\)
  3. C \(\vec{B}\) is anti-parallel to \(\vec{V}\)
  4. D \(\vec{B}\) is inclined to \(\vec{V}\) by \(45^\circ\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\vec{B}\) is perpendicular to \(\vec{V}\)

Step-by-step Solution

Detailed explanation

According to the Biot-Savart law, the magnetic field \(\vec{B}\) produced by a charge \(q\) moving with velocity \(\vec{V}\) at a position vector \(\vec{r}\) is given by

\(\vec{B} = \dfrac{\mu_0}{4\pi} \dfrac{q(\vec{V} \times \vec{r})}{r^3}\)

The direction of the magnetic field \(\vec{B}\) is determined by the cross product \(\vec{V} \times \vec{r}\).

By the properties of the cross product, the resulting vector \(\vec{B}\) is always perpendicular to both the velocity vector \(\vec{V}\) and the position vector \(\vec{r}\).

Therefore, \(\vec{B}\) is perpendicular to \(\vec{V}\).

Answer: \(\vec{B}\) is perpendicular to \(\vec{V}\)