# Exam II Questions

Alt+F4 said:
one more,

http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/sp06 [Broken]

question 24.

i did this like 20 times in other exams, i dont know why it doesnt work here but

F= ILBSintheta = MG

(X)(.1)(.5) = (9.8)(1)
X = 196Amps, but the answer is 98 Amps what gives?
is this the same idea on how one side isnt really contibuitng?

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OlderDan
Homework Helper
Alt+F4 said:
is this the same idea on how one side isnt really contibuitng?
I thought you had already resolved this one (#24). For this one you only used one side of the loop when you should have used both sides. Both sides contribute to the torque, so only half the current you calculated is needed.

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OlderDan said:
I thought you had already resolved this one (#24). For this one you only used one side of the loop when you should have used both sides. Both sides contribute to the torqe, so only half the current you calculated is needed.
silly me, thanks alot for your help like seriously. My TA's arent even that helpful

Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa05 [Broken]

So i tried doing it on Calculator but since sin180 = 0 i get 0
hmm all right so i graphed this, Does it matter if calc is in radian or degree?

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http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/su06 [Broken]

Question 20
Finger Curl with current
B Field points Down

I woulda picked Rotates it so that the right side comes out of the page and the left goes in.

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All right last question untill Nov 23rd i think

http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa03 [Broken]

Question 21

So W = 2piF = (2*3.14*580*10^3) = 3.6E6
>and 1 / ( sqrt 1*10^-3 * .06*10^-6) = 1.2909 E5

what am i doing wrong

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OlderDan
Homework Helper
Alt+F4 said:
All right last question untill Nov 23rd i think

http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa03 [Broken]

Question 21

So W = 2piF = (2*3.14*580*10^3) = 3.6E6
>and 1 / ( sqrt 1*10^-3 * .06*10^-6) = 1.2909 E5

what am i doing wrong
You are supposed to be finding the value of C that will make the resonant frequency of the circuit the desired broadcast frequency. How does C affect the net capacitance of the circuit?

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OlderDan
Homework Helper
Alt+F4 said:
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/su06 [Broken]

Question 20
Finger Curl with current
B Field points Down

I woulda picked Rotates it so that the right side comes out of the page and the left goes in.
Currents parallel to magnetic fields experience no force. Currents at right angles do.

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OlderDan
Homework Helper
Alt+F4 said:
hmm all right so i graphed this, Does it matter if calc is in radian or degree?
Yes. Always use radians for these time dependent problems. If they ask for phase in degrees, convert it from radians. If they give phase in degrees, convert it to radians. Angular frequency is always in radians/sec.

OlderDan said:
Yes. Always use radians for these time dependent problems. If they ask for phase in degrees, convert it from radians. If they give phase in degrees, convert it to radians. Angular frequency is always in radians/sec.
all right but for some reason when i graph in Radian mode i seriously get like -6 and -5 values unless i am doing something wrong with it

All right i need a CLarifcation on this one
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/sp06 [Broken]

Question 21

The angle i pick should be what to the field line? i wanted to do 90-22.5 but that wont work. Thanks alot

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Last Problem then im off to exam, Thanks Olderdan and whoever else that helped me. Really appreciate it

http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa05 [Broken]

Question 8

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OlderDan
Homework Helper
Alt+F4 said:
All right i need a CLarifcation on this one
http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/sp06 [Broken]

Question 21

The angle i pick should be what to the field line? i wanted to do 90-22.5 but that wont work. Thanks alot
Rotate through the small angle from the direction of v to the direction of B. It is just 22.5

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OlderDan
Homework Helper
Alt+F4 said:
Last Problem then im off to exam, Thanks Olderdan and whoever else that helped me. Really appreciate it

http://online.physics.uiuc.edu/cgi/courses/shell/phys102/fall06/prep2a.pl?practice/exam2/fa05 [Broken]

Question 8
Flux is
Φ = BAcosθ where θ is the angle between the loop normal and B. θ = 30 degrees

The only thing changing is B, so

dΦ/dt = (Acosθ)dB/dt

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Can't you take the exam for me?

OlderDan
Homework Helper
Alt+F4 said:
Can't you take the exam for me?
What exam are you taking? Could I bring all my reference materials with me? I still remember how to do this stuff, but it sure is nice having the references readily available when you don't remember the exact formulas, values of constants, etc.

OlderDan said:
What exam are you taking? Could I bring all my reference materials with me? I still remember how to do this stuff, but it sure is nice having the references readily available when you don't remember the exact formulas, values of constants, etc.
nope no refrence but u could program ur calculator. Im takin physics exam in like 2 hrs.