Question

The diagram above shows a negatively charged ball moving to the right below a wire carrying conventional current to the right. Both are in the plane of the screen.
What is the direction of the force on the negatively charged ball at the place it is pictured?

• A. up toward the top of the screen
• B. down toward the bottom of the screen
• C. toward the left side of the screen
• D. toward the right side of the screen
• E. The force is zero, since the negative charge is moving parallel to the current.

Answer 1

Answer: (B)

down toward the bottom of the screen

The direction of magnetic field lines in the region right to the current carrying wire where the negative charge is moving will be perpendicularly inward the page according to the right thumb rule .

The direction of movement of negative charge can be taken as the direction opposite to the direction of current . As the negative charge is moving toward right therefore the direction of current will be toward ,right , and magnetic field is perpendicular inward the paper so according to Fleming's left hand rule , force on positive charge will be down toward the bottom of the page .