Ampere's Law to find the magnitude of the magnetic field

AI Thread Summary
The discussion focuses on using Ampère's law to calculate the magnetic field generated by two parallel wires carrying currents of 12 A and 28 A at a distance of 0.72 m. When the currents flow in the same direction, the magnetic field is calculated to be -2.11 x 10^-5 T, indicating a specific direction based on the right-hand rule. For the scenario where the currents are in opposite directions, the magnetic field calculation requires changing the subtraction to addition in the formula. The final calculation for the magnetic field in this case remains to be completed. The thread emphasizes the importance of correctly applying Ampère's law to determine the magnetic field's magnitude and direction.
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Homework Statement


The wire in Figure 21-40 carries a current of 12 A. Suppose that a second long, straight wire is placed right next to this wire. The current in the second wire is 28 A. Use Ampère’s law to find the magnitude of the magnetic field at a distance of r = 0.72 m from the wires when the currents are (a) in the same direction and (b) in opposite directions.

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I1=12A
I2=28A
r= .72m
Mo= 4pi x 10^-7

Homework Equations


B = Mo/2(I1/pi(r)-I2/r)

The Attempt at a Solution


a.)

B= (4pi x 10 ^-7)/2 * (12/pi(0.72m)-28/.72m)
B=-2.11 x 10^-5 T

b.) not done yet
 
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in (a) current is in same direction ... so add them
 
cupid.callin said:
in (a) current is in same direction ... so add them

So just change the sign - to sign + in [i2/pi(0.72m) - 28A/.72m)]

how about in letter B?
 
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