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Unformatted text preview: 4 2/19 24 03 2013 HW- 5 Par t A
Find , the elec tric field ins ide the c ube. Ex pre ss the e le ctric fie ld in te rm s of , , a nd unit ve ctors ( , , a nd/or ). Hin t 1. Net force on charges in a conductor
Elec trons in a c onduc tor are more or les s free to move within the c onduc tor. As a res ult
elec trons in a c onduc tor plac ed in an elec tric field (with no magnetic field pres ent) will move until
the elec tic field that they generate ins ide the c onduc tor c anc els the applied field (i.e., until the
net internal elec tric field equals z ero). In general, the c harges in a c onduc tor move until the net
forc e on them is z ero. This happens almos t ins tantaneous ly in a good c onduc tor.
In this problem, there is no ex ternal elec tric field but there is a forc e on the elec trons due to the
applied magnetic field. The elec trons will thus move in s uc h a way as to c reate an elec tric field
that will c anc el the magnetic forc e on them (leaving a net forc e of z ero on the elec trons ). Hin t 2. F ind the magnetic force magnitude
W hat is , the magnitude of the forc e due to the magnetic field ex erted on an elec tron with c harge ins ide the c ube? Ex pre ss your a nsw e r in te rm s of som e or a ll of the va ria ble s , , a nd . ANSW ER:
= Hin t 3. F ind the magnetic force direction
Us e the vec tor equation and the right-hand rule to determine the direc tion of the forc e from the magnetic field. Remember to us e
Answ e r in te rm s of the unit ve ctors , , a nd for the elec tron c harge.
. ANSW ER: Hin t 4. Determine the force due to the electric field
W hat is , the forc e on an elec tron ins ide the c ube with c harge elec tric field due to an induc ed ? Ex pre ss your a nsw e r in te rm s of one or both of the va ria ble s a nd . ANSW ER: session.master ing physics.com/myct/assig nmentPr intView?assig nmentID= 2252604 3/19 24 03 2013 HW- 5 = ANSW ER:
Now, ins tead of elec trons , s uppos e that the free c harges have pos itive c harge . Ex amples inc lude "holes "
in s emic onduc tors...
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