Since a current carrying conductor in a magnetic field forces act, it, obviously, if you move this wire, they performed the work. Find out, what determines this work.

Attach two copper rod to the source of electrical energy (rice. 22.19) and lock them in a moving conductor l. Then in the circuit will go current I. Will create in the surrounding space perpendicular to the plane of the loop a uniform magnetic field with induction In (in figure. 22.19 induction line is directed to the reader and are represented by points). The conductor l will act ampere force F_A, and he will begin to move to the right (show, that right). Calculate the work when moving conductor l by the distance b.

Since in this case the direction of force and displacement coincide, and since F_A=ВIl, we have:

A=F_Ab=BIlb

If the area, covered by closed circuit (rice. 22.19), when the initial position of the conductor l are denoted by S₁ and at its end position—after S₂, then ΔS= S₂— S₁ there is an area change, covered by the current, when you move a conductor l. In figure. 22.19 see, that ΔS = lb, so:

A=ΔS IB.

Denoting the product of the BS via the f (Greek. "Phi"), get:

ВΔS = B(S₂— S₁)=BS₂—BS₁=F₂—F₁=DF.

So, the work when moving a conductor with current in magnetic field is expressed by the formula

А = IΔФ. (22.10)

Find out the physical meaning of the magnitude of f. Because the value is numerically equal to the number of lines of induction, passing through unit area SꞱ, perpendicular to them, then f=BSꞱесть total number of lines of the magnetic field penetrating the area SꞱ, if the induction At all points on the surface SꞱодинакова. The value of f is called magnetic flux or flux vector through the surface In SꞱ.

So, when a uniform field of magnetic flux is measured by the work on SꞱ:

Ф=ВSꞱ (22.11)

Note, the magnetic flux f is a scalar value. Derive the unit of magnetic flux in SI:

F = 1 T*1 m²=1 T*m²=1 kg*m2/ (with²*And) = 1 WB.

The SI unit accepted the f Weber (WB). Weber is the magnetic flux, which is spread perpendicular to the lines of induction in the surface 1 m² when the magnetic field induction in 1 TL.

Note, that according to the formula (22.10) it is possible to calculate the work, performed when turning a contour with a current in a magnetic field (DF indicates the change in magnetic flux, penetrating the circuit).