Question

In Figure P19.2, assume that in each case the velocity vector shownis replaced with a wire carrying a current in the direction of thevelocity vector. For each case, find the direction of the magneticforce acting on the wire.
(a) ---Select---into the pageto the rightto the leftdownwardupwardout of the page
(b) ---Select---into the pageout of the pagedownwardupwardto the rightto the left
(c) ---Select---to the leftinto the pageupwarddownwardto the rightout of the page
(d) ---Select---downwardout of the pageinto the pageto the leftupwardto the right
(e) ---Select---into the pageout of the pageupwardto the leftto the rightdownward
(f) ---Select---into the pageupwardout of the pageto the rightdownwardto the left

Answer 1

A) to the left

B) into the page

C) out of the page

D) up

E) into the page

F) out of the page

now you need help with the right hand rule:

this is nothing more than a visualization of ALL cross productvectors

You learned that

F_B=qv x B

(wire)F_B=(qv x B)nAd  

(wire)F_B=Id x B

(wire) dF_B= I (ds x B)

where ds is the vector in direction of the current in thewire.

Now your index finger fully stretched always represents thefirst component of you cross product. In this case it wouldrepresent ds. your middle finger(bent in a little) representsthe second component of your cross product. This would be your B(magnetic field). Your resulting vector is your thumb fullystretched out. In this case it would be your force