Zusammenfassung der Ressource
Ampere’s Law
- First discovered by André-Marie Ampère in
1826
- Definition: The integral around a closed path of
the component of the magnetic field tangent to
the direction of the path equals µ0 times the
current intercepted by the area within the path
- Or, in a simplified scalar form:
- Thus the line integral (circulation) of the magnetic
field around some arbitrary closed curve is
proportional to the total current enclosed by that
curve
- exercise: If we know that an electric current of 12
A flows through an empty 5 cm solenoid and the
magnetic field created inside it is 0.1 T. How many
turns is the solenoid made up of?
- To determine the number of turns,
it suffices to apply the formula of the
magnetic field generated inside a
solenoid and replace the values that
we know:
- Bibliography:
https://web.iit.edu/sites/web/files/departments/academic-affairs/academic-resource-center/pdfs/Amperes_law.pdf
-
http://hyperphysics.phy-astr.gsu.edu/hbasees/magnetic/amplaw.html#c2
- In order to apply Ampère’s Law all
currents have to be steady (i.e. do not
change with time)
- Only currents crossing the area inside
the path are taken into account and have
some contribution to the magnetic field
- Currents have to be taken with their
algebraic signs (those going “out” of the
surface are positive, those going “in” are
negative)- use right hand’s rule to
determine directions and signs
- The total magnetic circulation is zero
only in the following cases: -the
enclosed net current is zero -the
magnetic field is normal to the selected
path at any point -the magnetic field is
zero
- Ampère’s Law can be useful when
calculating magnetic fields of current
distributions with a high degree of
symmetry (similar to symmetrical
charge distributions in the case of
Gauss’ Law)
- Applications of the Ampere Law
- Magnetic Field of a Solenóide
- Magnetic Field of a Toróide
- The toróide is a very useful device
that is used in many areas, from tape
heads to tokamaks.
- Magnetic Field by Current
- Magnetic Force Between Cables