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Magnetic Field with three parallel wires

by rikinmathur
Tags: field, magnetic, parallel, wires
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rikinmathur
#1
Dec1-12, 02:15 AM
P: 1
1. The problem statement, all variables and given/known data
Three long, straight wires are carrying currents that have
the same magnitude. In C the current is opposite to that
in A and B. The wires are equally spaced. Each wire experiences a net force due to the other two wires. Which
wire experiences a net force that has the greatest magnitude?

A =====>====
B=====>====
C=====<====

2. Relevant equations
FAB = μI1 I2 / 2∏d


3. The attempt at a solution
It says that the answer is B because 2I squared / d is the net force on B. But the way I am doing it is -I^2/d + I^2/d = 0, hence the net forces cancel out and the force on B is zero. I don't understand how it is 2I^2/d. Please help.
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Pranav-Arora
#2
Dec1-12, 07:19 AM
P: 3,806
Hi rikinmathur! Welcome to pf!

What are the direction of forces on wire B due to the other two wires?
Tarti
#3
Dec1-12, 10:48 AM
P: 11
Hey rikinmathur, just think in terms of charges, maybe this is easier for you: A and B are positively charged (in a magnetic sense) and C is negative. So, which wire-pairs will experience an attractive and which a repulsive force?


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