Magnetic force Definition and 416 Threads

In physics (specifically in electromagnetism) the Lorentz force (or electromagnetic force) is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge q moving with a velocity v in an electric field E and a magnetic field B experiences a force of





F

=
q


E

+
q


v

×

B



{\displaystyle \mathbf {F} =q\,\mathbf {E} +q\,\mathbf {v} \times \mathbf {B} }
(in SI units). It says that the electromagnetic force on a charge q is a combination of a force in the direction of the electric field E proportional to the magnitude of the field and the quantity of charge, and a force at right angles to the magnetic field B and the velocity v of the charge, proportional to the magnitude of the field, the charge, and the velocity. Variations on this basic formula describe the magnetic force on a current-carrying wire (sometimes called Laplace force), the electromotive force in a wire loop moving through a magnetic field (an aspect of Faraday's law of induction), and the force on a moving charged particle.
Historians suggest that the law is implicit in a paper by James Clerk Maxwell, published in 1865. Hendrik Lorentz arrived at a complete derivation in 1895, identifying the contribution of the electric force a few years after Oliver Heaviside correctly identified the contribution of the magnetic force.

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  1. K

    How Is Magnetic Force Calculated on an Electron in a Uniform Field?

    Homework Statement An electron in a vacuum is first accelerated by a voltage of 48200 V and then enters a region in which there is a uniform magnetic field of 0.183 T at right angles to the direction of the electron's motion. What is the force on the electron due to the magnetic field...
  2. F

    Magnetic force with spring and resistor problem

    I am having a great deal of trouble solving the following problem. Can anyone help? A straight wire of mass 10.2 g and length 5.0 cm is suspended from two identical springs that, in turn, form a closed circuit (Fig. P19.66). The springs stretch a distance of 0.51 cm under the weight of the...
  3. F

    Solve for Magnetic Force with Unequal Length Wires | Quick Question

    Homework Statement Quick Question, you know that if two wires are 1 metre apart, both are 10 m long, they both carry 1 A, and the magnetic field they are in is 5 T, you would do the following to solve for force: F=(4pi x10^-7)(1A)(1A)(10m)/2pi*1 But what if the two wires are different...
  4. L

    Magnetic force: conservative or not?

    Hi, I was thinking, velocity dependent forces such as friction are considered non-conservative. The Lorentz force on a point charge moving in a constant magnetic field depends on its velocity, so it seems the magnetic force is non-conservative. Other criteria such as vanishing curl are also...
  5. S

    Magnetic Force of Wires: Solve Homework Equation

    Homework Statement A packed bundle of 100 long, straight, insulated wires forms a cylinder of radius R=.5cm a. if each wire carries 2A, what are the magnitude and direction of the magnetic force per unit length acting on a wire located .2cm from the center of the bundle? Homework...
  6. I

    Multiloop circuit, magnetic force on a current carrying wire, Ampere's Law

    1. Multiloop circuit In Fig. 27-71, R1 = 5.76 , R2 = 18.7 , and the ideal battery has emf = 13.8 V. (a) What is the size of current i1? http://img253.imageshack.us/img253/9926/fig2771dw3.gif Relevant equations i = V/R The attempt at a solution I redrew the 3 resistors (R2s) as...
  7. S

    How Can I Improve the Magnetic Force on a Conductor in My Physics Project?

    Homework Statement I am conceptualizing for a high school physics project and what I am currently trying to do is setup two ceramic magnets with opposite poles facing each other, but with a space in between. Next I have a wire running in between that is connected to a 1.5V power supply...
  8. N

    Magnetic force is a function of position?

    Sir,can you tell me if magnetic forces are function of position?Possibly,I read it somewhere in internet forums that magnetic forces are functions of velocity.I have read in your QM book's first page that---in microscopic level all type of force may be written as -∂V/∂x...except magnetic...
  9. mbrmbrg

    Magnetic Force to balance out Electric Force

    Homework Statement In the figure (see attatched), an electron accelerated from rest through potential difference 2.0 kV enters the gap between two parallel plates having separation 20.0 mm and potential difference 130 V. The lower plate is at the lower potential. Neglect fringing and assume...
  10. E

    Magnetic Force, Resistance, Faraday's Law

    Homework Statement A conducting bar of length L = .218 m and mass M = .08 kg lies across a pair of conducting rails. The contact friction between the bar and the rails is negligible, but there is a resistor at one end with a value R = 20.0 Ohms. Initially the rod is given an initial speed of v0...
  11. S

    Magnetic Force and Two Moving Charges

    Homework Statement A pair of point charges, q = 7.60 microC and q' = -4.50 microC, are moving in a reference frame, as shown in the figure, with speeds 9.00×10^4 m/s and v' = 6.40×10^4 m/s. a. When the point charges are at the locations shown in the figure, what magnetic force...
  12. X

    How Does Voltage Influence Electron Motion in a Magnetic Field?

    An electron is accelerated through 2550 V from rest and then enters a region where there is a uniform 1.70 T magnetic field. What are the maximum and minimum magnitudes of the magnetic force acting on this electron? F = qvB F = (mv^2)/R F = qE I know q = 1.6*10^-19, B = 1.7, and V = 2550. In...
  13. S

    Velocity Components and Magnetic Force

    Homework Statement A particle with charge 9.42×10−8 C is moving in a region where there is a uniform magnetic field with a magnitude of 0.440 T in the +x-direction. At a particular instant of time the velocity of the particle has components -v_x = 1.70×10^4 m/s, -v_y = 3.19×10^4 m/s, v_z...
  14. C

    How Do You Calculate the Angle of the Net Magnetic Force in a Complex Field?

    One component of a magnetic field has a magnitude of 0.074 T and points along the +x axis, while the other component has a magnitude of 0.020 T and points along the -y axis. A particle carrying a charge of +7.50 10-5 C is moving along the +z axis at a speed of 3.20 103 m/s. (a) What is the...
  15. D

    What Is the Angle of the Rod in the Magnetic Field?

    1. Homework Statement a thin, uniform rod, which has a length of 0.45 m and a mass of 0.080 kg. This rod lies in the plane of the paper and is attached to the floor by a hinge at point P. A uniform magnetic field of 0.25 T is directed perpendicularly into the plane of the paper. There is a...
  16. D

    Max. magnetic force on an electron

    Homework Statement In a television set, electrons are accelerated from rest through a potential difference of 17 kV. The electrons then pass through a 0.30 T magnetic field that deflects them to the appropriate spot on the screen. Find the magnitude of the maximum magnetic force that an...
  17. D

    Magnetic Force on Electron: Unanswered Mystery

    an electron moves within a uniform magnetic field of .2T at a speed of 5x10^5 m/s. What is the magnetic force on the electron? I used Fm=qvBSin and got 1.6x10^-14N but the answer is that it can't be determined with this info why not?
  18. A

    Why Does Magnetic Force Behave Differently with Charges Compared to Steel?

    hiya I assume the field lines represent the strength of magnetic field and show the direction of magnetic force. So if we put iron filings on paper with magnet near by, then fillings will arrange themselfs in such way to show the direction of the magnetic forces on these iron fillings...
  19. B

    Why do magnets attract or repel each other?

    If I have one magnet sitting on a table and I take another magnet and bring close to the first one it will move towards the magnet! This is amazing to me. My question is why does one magnet make another move toward or away from it? what is the origin of magnetic force. I think it has...
  20. S

    What is the current flowing through the aluminum rod on tilted conducting rails?

    The two conducting rails in the drawing are tilted upwards so they make an angle of 30.0° with respect to the ground. The vertical magnetic field has a magnitude of 0.055 T. The 0.22 kg aluminum rod (length = 1.6 m) slides without friction down the rails at a constant velocity. How much current...
  21. S

    Find the magnitude of the maximum magnetic force

    In a television set, electrons are accelerated from rest through a potential difference of 25 kV. The electrons then pass through a 0.26 T magnetic field that deflects them to the appropriate spot on the screen. Find the magnitude of the maximum magnetic force that an electron can experience...
  22. S

    Can SR fully explain magnetic force?

    As we know for over 100 years magnetic force in an relativistic effect caused by the movement of charged particles. Let’s take the standard example - current in a wire. If a charged test particle (say electron) is moving relative to the wire it feels the Lorentz force. I can understand...
  23. F

    Calculating Magnetic Force on a Current-Carrying Wire

    Hello guys I have the following problem : At a certain location, Earth has a magnetic field of 8.4 X 10^-5 T pointing 40 degree below the horizontal in a north-south plane. A 14.1m long straight wire carries a(n) 7 A current. If the current is directed horizontally toward the east, what...
  24. S

    Max Magnetic Force Experienced by Electrons Accelerated at 19 kV

    In a television set, electrons are accelerated from rest through a potential difference of 19 kV. The electrons then pass through a 0.29 T magnetic field that deflects them to the appropriate spot on the screen. Find the magnitude of the maximum magnetic force that an electron can experience...
  25. P

    What is the Magnitude of the Force on a Wire in a Uniform Magnetic Field?

    A current of 3.1 A flows in a straight wire segment length (4 cm)i + (5 cm)j in a uniform magnetic field of strength (0.9 T) i. Find the magnitude of the force on the wire. Answer in units of N. First I found the magnitude of the length of the wire, \sqrt .04^2 +.05^2 = .0640 m. Then I...
  26. P

    How Does Magnetic Force Affect a Charged Metal Ball in Motion?

    A metal ball having net charge 8.9e-6 C is thrown out of a window horizontally at a speed 47 m/s. The window is at a height 89 m above the ground. A uniform horizontal magnetic field of magnitude 0.03 T is perpendicular to the plane of the ball's trajectory. Find the magnitude of the magnetic...
  27. K

    How Does Current Affect Magnetic Force and Torque in a Rotating Loop?

    I have a question here A rectangular plane loop with dimensions 250 mm by 180 mm is pivoted to rotate about the z axis. The long side of the loop is along the y-axis and the plane of the loop makes an angle of 45 degrees with the y-axis. If a uniform magnetic field of magnitude 300 mT is in...
  28. K

    How Do Weight and Magnetic Force on an Electron Compare Near Earth's Surface?

    How can I Compare the magnitudes near the earth’s surface of the weight of an electron and a typical magnetic force exerted by the earth’s magnetic field (B = 10-5T) on an electron with speed 10 m/s. As I understood Weight of electron = mg Magnetic force=qBv am I right?
  29. U

    Finding magnetic force on two different segments

    I've been having some trouble with this homework problem: There is a semicircular current loop that lies in the xy plane. The straight segment "a" of of the loop has length 2R while the semicircular segment "b" has radius R. There is a magnetic field of strength B into the page. Current I is...
  30. D

    The Hall effect and the magnetic force on current carrying wires

    As I understand it, a current flowing through a conducting strip in a magnetic field perpendicular to the current will drift to the side creating an electric field that corrects the currents motion and creates a potential difference across the conductor. Why then does a current carrying wire in...
  31. E

    Magnetic Force from an EM Wave

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  32. L

    What's the magnitude of the magnetic force acting on the particle?

    hey physics experts could you help me out with these two problems please? 1/ A positively charged particle of mass 5 x 10^-5 kg is traveling due east with a speed of 80 m/s and enters 0.3 T uniform magnetic field. The particle moves through one quarter of a circle in a time of 2 x 10^-2s, at...
  33. M

    I got the formula, what does the angle effect? Net Magnetic force

    Hello everyone, I think I am missing this problem because there is an angle invovled, but it doesn't seem to matter what angle it is from what my lecture notes say. but here's the question: The bent wire shown in Fig. 28-39 lies in a uniform magnetic field. Each straight section is 2.1 long and...
  34. K

    What Angle Gives a Magnetic Force of 1.8 Times the Original Force?

    When a charged particle moves at an angle of 19° with respect to a magnetic field, it experiences a magnetic force of magnitude F. At what angle (less than 90°) with respect to this field will this particle, moving at the same speed, experience a magnetic force of magnitude 1.8F? can...
  35. B

    What Determines the Smallest Orbit Radius for a Proton in a Magnetic Field?

    Question: What is the radius of the smallest possible circular orbit that a 2MeV proton can have in a 2 T magnetic field? Answer (what I've got so far, at least): I assume that r = mv/qB is the formula I use for this problem, due to being given mass, B, q and all that, but I can't...
  36. M

    Magnetic Force: Halving the Distance

    Am I correct in assuming that if the distance between two poles of different magnets is halved, then the force of repulsion (or attraction) will increase while the attraction (or repulsion) will decrease? If the distance is halved, isn't the force quadrupled? Thanks.
  37. T

    Why Does Magnetic Force Not Alter the Speed of a Charged Particle?

    why is the magnitude of velocity of a charged particle not affected by magnetic force? :bugeye:
  38. P

    Asking about direction of magnetic force

    I have a problem with a question that asked me to give the direction of magnetic force of a long wire with a current flowing from west to east horizontally with a magneitc field pointing into the page. What is the direction of the force and the motion afterwards?
  39. C

    What is the Formula for Magnetic Force in Electromagnets?

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  40. T

    Help Solving a Problem with Cylindrical Wires: Magnetic Force Calculation

    Could anyone please help me with the following problem? A compact package contains n = 100 long straight wires, shaped like a cylinder with a radius of R = 0.500 cm. If each wire conducts i = 2.00 A, calculate the intensity and direction of the magnetic force per unit of length acting on a...
  41. O

    Understanding the Relationship Between Angle and Magnetic Force

    Hi, I am having trouble with my last physics homework question (below): When a charged particle moves at an angle of 16° with respect to a magnetic field, it experiences a magnetic force of magnitude F. At what angle (less than 90°) with respect to this field will this particle, moving at the...
  42. E

    How Do You Calculate Magnetic Force in Three Dimensions?

    Hello. I am currently working on this problem: "An electron moves in the X-Y plane with a velocity v = (5 *10^5 m/s , 30 degrees). The uniform magnetic field i the region is B= ( 6 i - 2 j + 1 k ). Find the resultant magnetic force on the electron in component form." I know that F = qv...
  43. N

    Order of magnitude of the magnetic force

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  44. M

    How Do I Calculate the Magnetic Force on a Coil from a Circular Ring?

    I'm stuck on the following problem: A long thin coil of length l, cross-sectional area S, and n turns per unit length carries a current I. It is placed along the axis of a large circular ring of radius a, which is carrying a current I'. If d is the displacement of the center of the coil from...
  45. B

    Finding Magnetic Force on a Moving Electron

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  46. R

    How Is Magnetic Force Calculated on a Cylinder in a Gradient Field?

    I am a chemistry student that is trying to calculate the magnetic force on a cylinder due to a gradient produced by sitting in an annulus. The annlus is a cylinder of height h with outer radius ro and inner radius ri. The other cylinder has height h and radius r such that a gap exists with...
  47. E

    How Is the Direction of Magnetic Force Determined in This Scenario?

    Hi, I have a question: If there is a negative charge moving w/a velocity that is 50 degrees counter-clockwise from the +x-axis and a B field in the +z direction, I get that the magnitude of the Magnetic Force=(abs. val of q)(abs. val of v)(abs. val of B)sin(theta), where theta=angle b/t v and B...
  48. F

    Magnetic Force: Calculating B for 4.01A Wire

    The x, y, and z components of a magnetic field are Bx=0.193 T, By=0.233 T, and Bz=0.263 T. A 29.5 cm wire is oriented along the z axis and carries a current of 4.01 A. What is the magnitude of the magnetic force that acts on this wire? how do i calc my B cuz i know f=4.01A/(0.295m)(?T)(sin90)
  49. T

    How Does Magnetic Force Affect an Ion Moving Along the Line x=y?

    Ok, an ion experiences a magnetic force of 6.2X10^-16 N when moving in the positive x direction, but no force when moving in the positive y direction. What is the magnitude of magnetic force exerted on the ion when it moves in the x-y plane along the line x=y? Assume the ions speed is the same...
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