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Fisikastudycenter.com- learning magnetic force on straight conductors in 6 common problems, how to determine the magnitudes and the directions of the forces, right hand rules and parallel conductors interaction wiill be discussed through questions and answers method.

Problem 1
A straight wire carries a current of 5 A placed between two poles of magnets. If the amplitude of magnetic field is o,or Tesla then find:

Note: U = utara = north, S = selatan = south, B = barat = west, T = timur = east

a) magnetic force acts on the wire with 10 cm in length
b) direction of magnetic field


Asnwer
a) The magnetic force acts on a conductor with length l meter in a magnetic field B Tesla carries a current of i Ampere with an angle between B and i is θ found by an equation F = Bil sinθ , insert the data to the equation then we get :



b) magnetic force direction with right hand rules
4 fingers → B direction
thumb→ i direction
palm → F direction

The magnetic field direction comes from north pole to south pole of a magnet, so then the direction of F is into the plane of the figure or down if we use the compass direction reference above.

Problem 2
Given a straight current-carrying conductor on a magnetic field below



Where is the direction of magnetic force acts on the conductor?

Answer
By using the right hand rules we get the direction is out of the plane of the figure.

Problem 3
Given two conductors as show in the below figure!



Find the magnitude of magnetic force acts on the second wire with a lenght of 0.5 meter!

Answer
The equation for magnetic force on two parallel wires as shown the figure above separated by length l is :



Force direction:
If the direction of the currents in both conductors are the same, the two conductors will attract each other
If the currents in both conductors are opposite, the two conductors will repell each other

So then the magnetic force on second wire is to the left.

Problem 4
Three straight conductors are arranged as below!



Find the magnetic force acting on the second wire for 1 m of length!

Answer
a) There are two magnetic forces acting on the second wire from its interaction with the first and the third wires.

The force from wire I named F₂₁ :



The direction is to the left

The force from wire III, named F₂₃ :



The direction is to the left also.

The resultant named F₂:



The direction is to the left

Problem 5
A and B is 2 meter apart with the currents respectively 1 A and 2 A.



Where is the location of wire C so the magnetic force acts on it is zero?

Pembahasan
Locate C on the place where the direction of magnetic force from the two others are in opposite direction. The possible location is at the left of Aor at the right of B. Try the firs location, name the distance to wire A is x



The result is 2 meter at the left of wire A or 4m of wire B.

Problem 6
Three conductors form an equilateral triangle shown the figure below! The current direction of wire A is out of the plane of the figure, in B and C are into the plane of the figure.



Find:
a) the magnetic force acts on conductor B in a length of 1 m
b) the direction of the force

Answer
a) the figure of forces acting on conductor B with the angles



Finding F_BA :



Finding F_BC :



The resultant named F_B:



Insert your data :



b) Using vectors components to get the direction of the resultant :





The result is 60^o .