A particle of charge $q$ and velocity $v$ passes undeflected through a space with non-zero electric field $E$ and magnetic field $B$. The undeflecting conditions will hold if.

  • A

    signs of both $q$ and $E$ are reversed.

  • B

    signs of both $q$ and $B$ are reversed.

  • C

    both $B$ and $E$ are changed in magnitude, but keeping the product of $|B|$ and $|E|$ fixed.

  • D

    both $B$ and $E$ are doubled in magnitude.

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