2005 15a) (1 Viewer)

[dolbinau]

A current is passed along a square semiconductor rod as shown. Half of the current is
carried by electrons and half by holes. A magnetic field is then applied to the rod at right
angles to its axis.
Which of the following correctly describes the movement of the electrons and holes in
the rod when the magnetic field is applied?
(A) They speed up.
(B) They slow down.
(C) They move to the same side of the rod.
(D) They move to opposite sides of the rod.


There is a diagram which you will probably need here:

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2005exams/pdf_doc/physics_05.pdf

But. The answer is C) Apparently they both move down but I don't get it.

Using Right hand palm, conventional current (holes?) would experience a force down, but wouldn't electrons experience a force up because of the opposite direction?

 

[Lucid Scintilla]

Using the RHPR, it is shown that there's a force acting downwards on the conventional current. Sure the holes move in the opposite direction to the electrons; but they're also opposite in charge, so both the current and the electrons will move to the bottom of the rod.
Thus, (C).

Edit: Too long; didn't read?
It sort of cancels out.

 

[dolbinau]

Oh I get it, thanks.