Magnetic field between two parallel wires

AI Thread Summary
The problem involves calculating the equal currents in two parallel wires that create a magnetic field of 300 µT halfway between them, with the wires spaced 8 cm apart. The formula used is B = (μ * I) / (2 * π * distance), where the distance is halved to 0.04 m. The initial calculation yielded 60 Amperes, but the correct approach considers the contributions from both wires, leading to the conclusion that each wire must carry 30 Amperes. For antiparallel currents, the magnetic fields cancel, while for parallel currents, they combine, reinforcing the total magnetic field. Thus, the correct current in each wire is 30 Amperes.
fishingspree2
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Homework Statement



Two parralel wires are 8 cm apart. The magnetic field halfway between them is 300 uT. What equal currents must be in the wires? Consider parralel and antiparralel currents

Homework Equations


I use Ia=Ib

B = (u*i) / (2*Pi*distance) where distance = 0.04 m (0.08m divided by two since it is halfway)

then I solve for I, I get 60 Amperes, the answers is 30 amperes

What to do?
 
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Maybe you are not taking into account that the magnetic field is due to the current of _two_ wires
 
Note that the forces on these two wires will attract each other, combining together and forming double the magnetic field because the fields are in the same direction :)
 
I think that it is correct for anti-parallel case. 30 A for each wire.
 
you have to consider currents for both wires. so in this case current will b 2i.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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