Electromagnetic Forces and Fields: Ranking, Ratio, and Distance Calculations

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The discussion revolves around the calculations and principles of electromagnetic forces and fields related to current-carrying wires. Participants analyze the forces on three equally spaced wires with different current directions, noting that symmetry affects the forces experienced by the outer wires. The magnetic field produced by long straight wires is discussed, emphasizing the need to understand the direction and magnitude of the fields based on current direction. Key points include the effects of parallel and antiparallel currents on the magnetic field at specific points and the dependence of the magnetic field strength on distance from the wire. Overall, the conversation highlights the importance of foundational concepts in electromagnetism for solving related problems.
nautica
11) the diagram shows 3 equally spaced wires that are perpendicular to the page. the currents are equal, 2 being out of the page and 1 going into the page. rank the wires according to the magnetude of the forces on them, from least to greatest.


. x .
1 2 3

12) A proton (charge e) traveling perpendicular to a mag field, experiences the same force as an alpha particle (charge 2e) which is also traveling perpendicular to the same field. the ratio of their speeds, v (proton) / v (alpha)

My answer is 2

13) the mag field in T a distance of 2 cm from a long straight wire carrying a current of 2 A is about

15) 2 long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the mag field they produce is?

a) zero ( I picked a)
b) non-zero and along a line connecting the wires
c) non-zero and parallel to the wires
d) non-zero and perpendicular to the plane of the two wires
e) non of the above

16) 2 long strait wires are parallel and carry current in the same direction. the currents are 8 A and 12 A and the wires are separated by .4 cm. the mag field in tesla at a point midway between teh wires is?

18) the mag field outside a long straight current-carrying wire depends on the distance R from the wire axis according to
a) R
b) 1/R
C) 1/R^2
d) 1/R^3
e) 1/R^3/2
 
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Field from a current-carrying wire: Learn it!

Originally posted by nautica
11) the diagram shows 3 equally spaced wires that are perpendicular to the page. the currents are equal, 2 being out of the page and 1 going into the page. rank the wires according to the magnetude of the forces on them, from least to greatest.


. x .
1 2 3

No. First note the symmetry between the left and right wires: they must experience the same force. Now find the B field that they exert on the middle wire.
12) ...
My answer is 2
OK.
13) the mag field in T a distance of 2 cm from a long straight wire carrying a current of 2 A is about
Learn the expression for the field produced by a current carrying wire; look it up.
15) 2 long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the mag field they produce is?

a) zero ( I picked a)
b) non-zero and along a line connecting the wires
c) non-zero and parallel to the wires
d) non-zero and perpendicular to the plane of the two wires
e) non of the above
No. Once again, you must know the field produced by a current-carrying wire. No calculation is needed here, but you do need to know what direction the field points. Compare with #11
16) 2 long strait wires are parallel and carry current in the same direction. the currents are 8 A and 12 A and the wires are separated by .4 cm. the mag field in tesla at a point midway between teh wires is?
Same comment.
18) the mag field outside a long straight current-carrying wire depends on the distance R from the wire axis according to
a) R
b) 1/R
C) 1/R^2
d) 1/R^3
e) 1/R^3/2

Ditto.
 
On #18

B= uI/2pieR

So the answer should be 1/R. Right?

Nautica
 
I am confused about this one.

15) 2 long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the mag field they produce is?

a) zero
b) non-zero and along a line connecting the wires
c) non-zero and parallel to the wires
d) non-zero and perpendicular to the plane of the two wires
e) non of the above
 
On #11 the 1,2,3 were the names of the wires. I forgot to include my answer

2 would have the greatest and 1 and 3 would be tied. right?
 
Originally posted by nautica
I am confused about this one.

15) 2 long parallel straight wires carry equal currents in opposite directions. At a point midway between the wires, the mag field they produce is?

a) zero
b) non-zero and along a line connecting the wires
c) non-zero and parallel to the wires
d) non-zero and perpendicular to the plane of the two wires
e) non of the above


d
 
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