Question

4.2.2 quiz: electromagnetism
question 1 of 10
why do electric charges that move through a magnetic field produce an electric current?
a. the magnetic field pushes negative charges and positive charges in opposite directions.
b. the magnetic field exerts a force on only the positive charges in the wire.
c. the magnetic field exerts a force on only the negative charges in the wire.
d. the magnetic field pushes negative charges and positive charges in the same direction.

Explanation:

When electric charges move through a magnetic field, the magnetic field exerts a force on both positive and negative charges. According to the Lorentz force law \( \vec{F} = q\vec{v}\times\vec{B}\), where \(q\) is the charge, \(\vec{v}\) is the velocity of the charge, and \(\vec{B}\) is the magnetic field. For positive charges (\(q>0\)), the direction of the force is given by the right - hand rule for the cross - product \(\vec{v}\times\vec{B}\), and for negative charges (\(q < 0\)), the direction of the force is opposite to that given by the right - hand rule. So, the magnetic field pushes negative charges and positive charges in opposite directions. This separation of charges creates an electric current.

Answer:

A. The magnetic field pushes negative charges and positive charges in opposite directions.