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Tuesday, March 9, 2010

EM Worksheet guide

1. Use formula B= (F/L) I sin(90) to help you say it in words.
2. Follow the lecture notes and tutorial. Mainly use right hand to help you (NO name for this rule) Fingers curling can be B field for straight conductor. Fingers curling can be current for solenoid. For permanent magnet N pole ( arrows point out) and S pole (arrows point in).
3. Consider Current 1 , Use your right hand to show B1 at corner R. Show B2 due to current 2 at corner R . Show B3 due to current 3 at corner R. Find the resultant B by adding B1, B2 and B3 (vector addition). The direction is N 45 degrees E.
4. Show the B vector. If I is parallel to B , angle = 0 hence no force. If B vector is perpendicular to I , angle = 90 degrees , F= BIL , force is not zero.Use LHR.
b) Fprce = BIL = 0.048 N
5. Use LHR, Force is perpendicular to I (velocity of charge) hence circular motion .
v = Bqr/m . By equating magnetic force = centripetal force. The velocity = 8.8 x 10 7 ms-1.
6. Velocity selector v = E/B .
a) electric force up , hence magnetic force must be down . Hence B is into the plane
b) v = E/B , calc B. B = 125 T
c) If speed increases , magnetic force increases (Bqv)but electric force( qE) remain the same. Hence the magnetic force more than electric force , ions deflected downwards.