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 In a certain region static electric and magnetic fields exist.  The magnetic field is given by

 If a test charge moving with a velocity experiences no force in that region, then the electric field in the region, in SI units, is :


  • Option 1)

  • Option 2)

  • Option 3)

  • Option 4)


Answers (1)


As we learnt in

Magnetic field If V(vector), E (vector) and B (vector) are mutually perpendicular -





 \vec{B}= B_0(\hat{i}+2\hat j-4 \hat k), \:\vec v=v_0(3\hat i-\hat j+2\hat k)

\vec F= \vec F_e+\vec F_m

\therefore \vec F=0

\vec F_e= -\vec F_m\Rightarrow \vec F_e=-q(\vec v\times\vec B)

\vec F_e= -qv_0B_0(3\hat i-\hat j+2 \hat k)\times(\hat i+2 \hat j-4\hat k)

\vec F_e= -qv_0B_0(14 \hat j+7\hat k)

Electric field produced by the charge

\vec E=\frac{\vec F_e}{q}= -qv_0B_0\frac{(14 \hat j+7\hat k)}{q}= -v_0B_0(14 \hat j+ 7\hat k)

Option 1)

This is incorrect option.

Option 2)

This is incorrect option.

Option 3)

This is incorrect option.

Option 4)

This is correct option.

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