[Risolto] Campo magnetico

Es. 1

the two poles are of the same name: they can be either both south poles or north poles but you cannot say whether they are north or south. The relevant thing is that they are repelling each other. South attracts north and north attracts south, while north-north are repelling each other as south-south do.

Es. 2.

The exercise ask for creating a plot of the field lines:

remember: field lines exit from North poles and enter into South poles!

a) lines are always closed

b) already done (see arrows in the above plot)

c) 

 

es.9

the force between two parallel wires (conductors) crossed by 2 currents $i_1$ and $i_2$ and placed at a distance $d$ one from each other and long both $L$ is:

$F=\frac{\mu_0}{2\pi}\frac{i_1 i_2 L}{d}$

in our case $i_1=i_2$ and we can call them simply $i$

the constant $\frac{\mu_0}{2\pi}=2*10^{-7}$ therefore

$5*10^{-8}=2*10^{-7}\frac{i^2 0.6}{0.4}$ and thus

$\frac{5*10^{-8}*0.4}{2*10^{-7}0.6}=i^2$

 $i^2=0.166666$

$i=0.41 A$