# Want to compare multiple-choice answers? (1 Viewer)

#### fizzwizz

##### New Member
D is correct. Angle theta is misunderstood - it is the angle between the plane of the current (the page) and the plane of the magnetic filed (many parallel planes coming in or out of page) In this case that angle is 90 degrees. Use pythag (square root of (0.5 squared + 0.5 squared) to find L. Then use F=BIL (SIN 90) to give D

#### gamecw

##### Member
i got 9&10 wrong... so 13/15

#### Lachdog

##### New Member
eX-Bhai said:
that is incorrect. The answer is C

By using basic trig, Sin 45 = 0.4 / L
Therefore 0.4 = L.sin45

By using the formula F = BILsin@

B = 0.5 T
A = 3 A
Lsin@ = 0.4

Therefore F = 0.6 N
That is exactly why the answer is 7d. You said L.sin45 = .4. that means,

L=.4/sin45.
L=.5656.....
F=BIl
F=.5x3x.5656...
F=.849 N. Definately 7 d

#### hysteria85

##### New Member
Sweet according to the tabulated results above I got 15/15.

Are the 'correct' answers there just the most common ones? or have they been verified by a teacher or something?

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#### arkanisw

##### New Member
eX-Bhai said:
that is incorrect. The answer is C

By using basic trig, Sin 45 = 0.4 / L
Therefore 0.4 = L.sin45

By using the formula F = BILsin@

B = 0.5 T
A = 3 A
Lsin@ = 0.4

Therefore F = 0.6 N

owned.. that's what they WANT you to do. but it isnt, read the other posts comments about θ being 90 degrees.

sigh, tricky ppl those examiners. check out the post i set up "Things examiners want you to get wrong" for a list that you may also have got fooled in

#### carra330

##### New Member
shinji said:
but isn't it perpendicular to magnetic field?
hence, it starts off with max flux [sin@] and then decreases to 0 as it is parallel .. and yeah.

that's what it thought ~_~
hey

sorry to disappoint any of you who picked 8 a or b, the actual answer is c, as flux is not a vector quanity so it will never be negative, leaving the only answer/graph as c. Dont worry i was in the same arguement with half my class when we walked out, whether it started with max or min, and i thought b, but then our physics teacher stepped in and stood us all down and told us it was c, and that we were all wrong . And yes he is a reliable teacher, considering he got 99/100 for his extension maths test when he did school --FREAK!!!!

#### helper

##### Active Member
carra330 said:
hey

sorry to disappoint any of you who picked 8 a or b, the actual answer is c, as flux is not a vector quanity so it will never be negative, leaving the only answer/graph as c. Dont worry i was in the same arguement with half my class when we walked out, whether it started with max or min, and i thought b, but then our physics teacher stepped in and stood us all down and told us it was c, and that we were all wrong . And yes he is a reliable teacher, considering he got 99/100 for his extension maths test when he did school --FREAK!!!!
Maybe he should have a discussion with professor joseph f becker, san jose university
http://www.physics.sjsu.edu/becker/physics51/induction.htm