Torque on current loop and magnetic moment derivation with. Apr 10, 2018 a current carrying loop acts like a little magnet with north on one side of the loop and south on the other. Calculate the torque on a current carrying loop in a magnetic field. A magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the dimensions of the source are reduced to zero while keeping the magnetic moment constant. Calculate the magnetic torque magnetic torque on a coil or solenoid of area a, turns n, and current i in a given bfield. Top views of a current carrying loop in a magnetic field. Torque on currentcarrying loop in magnetic field motor. What current carrying loop experiences are in a magnetic. Apr, 2020 therefore, the loop has a net torque and rotates to the position shown in b. Clicker 1 torque on a current loop university of florida. Torque on current carrying loop definition, examples, diagrams. This is ia, where iis the current and the magnitude of a is the area aenclosed by the loop.
Torque on currentcarrying loop in magnetic field motor theory. If the loop has a width a, a height b, and a current i, then the force on each of the left and right sides is f ibb. Now we shall show that a steady current i passing through a rectangular loop placed in a uniform magnetic field. Physics mcqs for class 12 with answers chapter 4 moving. Calculate the magnetic field magnetic field induced at the center of a loop loop or coil coil or at the interior of a solenoid.
Jul 09, 2017 torque on a current carrying loop cross product of dipole moment vector and magnetic field vector magnetic moment of loopi. Amperes law solenoid material magnetism which of the following is wrong. Let us examine the force on each segment of the loop in figure 1 to find the torques produced about the axis of the vertical shaft. Magnetic force, torque, and magnetic moments objectives 1. Torque on current loop iconsider rectangular current loop forces in left, right branches 0 forces in topbottom branches cancel no net force.
How to find the torque on a current loop in a magnetic field 1. Physics mcqs for class 12 chapter wise with answers pdf download was prepared based on latest exam pattern. The torque exerted by the magnetic force including both sides of the coil is given by. Magnetostatics university of colorado colorado springs. No magnetic forces act on sides 1 and 3 because these wires are parallel to the.
What is the general proof that the torque acting on an. Torque on a current carrying rectangular loop in a magnetic. Students can solve ncert class 12 physics moving charges and magnetism mcqs pdf with answers to know their. A uniform magnetic field exerts no net force on a current loop but it does exert a net torque.
Similarly on the side da,no magnetic force acts since current element makes an angle. To start with the magnetic force on a moving charge q and derive the force on a wire segment carrying current i. Apparatus horseshoe magnet or pair of bar magnets, loop of wire attached to power supply. Chapter 19 21 a a b b torque on current loop iconsider rectangular current loop forces in left, right branches 0 forces in topbottom branches cancel no net force. Describe how motors and meters work in terms of torque on a current loop. A, i is current in the loop,a is its area and of course, torque at a pointr. This is the torque on a current carrying loop in a uniform magnetic field. The magnitude of the torque can be given by, torque on current loop the magnetic moment. A current loop may experience a torque in a constant magnetic field x b we can associate a potential energy with the orientation of loop u b z x y b 30 y z i initial final strategic analysis find calculate the change in potential energy from initial to final a b calculation a square loop of side a lies in the x z plane with current i as shown. The loop carries a current, has turns, each of area, and the perpendicular to the loop makes an angle with the field. Calculate the torque on a currentcarrying loop in a magnetic eld. Oct 31, 2019 free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 4 moving charges and magnetism. Each loop of current has a direction associated with it.
No torque acts on the loop, but the loop continues to spin from the initial velocity given to it in part a. They solve example problems as a class and use diagrams to visualize the vector product. If there is another magnet magnetic field below it the south pole at a will be attracted or repelled straight up or straight do. A currentcarrying loop of wire attached to a vertically rotating shaft feels magnetic forces that produce a clockwise torque as viewed from above. Torque on a currentcarrying coil in a magnetic field the dc direct current motor an application of the torque on a currentcarrying loop if the loop starts from rest in the orientation in figure 19. What is the general proof that the torque acting on an irregular current carrying loop in an uniform magnetic field is only dependent on area. What happens when we place a rectangular loop carrying a current i in the xy plane and switch on a uniform magnetic field. Magnetic torques and amps law a magnetic field exerts a force on a straight wire carrying current. Motors and meters openstax this work is produced by openstaxcnx and licensed under the creative commons attribution license 3. If the coil having n rectangular loop is placed in magnetic field then torque is given by. Force and torque on a current loop university physics.
How to find the torque on a current loop in a magnetic field. In the equation written earlier, we can see that the torque exerted on a current carrying coil placed in a magnetic field can be given by the vector product of the magnetic moment and the magnetic field. Motors are the most common application of magnetic force on current carrying wires. Torque on a current loop in a uniform magnetic field consider a rectangular loop carrying a current i in the presence of a uniform magnetic. Through the associated activity, get your motor running, students explore a physical model to gain empirical data and. Magnetic torques and amps law rochester institute of. Torque on a current loop, electrical motor magnetic field around a current carrying wire. What is the magnitude of the torque on the circular current loop in the figure. So, i suppose many comforts of modern life depend on this interaction. Torque on a current loop we showed that the net magnetic force on a closed current containing loop is zero when it is in a uniform magnetic field. Consider, for example, the current carrying rectangular loop of height, \h\, and width, \w\, immersed in a uniform magnetic field, \\vec b\, as illustrated in figure \\pageindex1\ note that the field is not perpendicular to the plane of the loop, as it was in example 21. The direction of a is perpendicular to the loop, in the direction given by the \ loop rhr. Forcetorque on a current loop due to its own magnetic field. Torque on current carrying loopdiploe moment of loop.
F the attempt at a solution i found out the dipole moment of the whole disc by integration,through the following method. Force and torque on a current loop physics libretexts. The torque on a current carrying coil, as in a dc motor, can be related to the characteristics of the coil by the magnetic moment or magnetic dipole moment. Torque on a current carrying loop printer friendly version remember that when a current carrying wire is placed in an external magnetic field then it will experience a magnetic force that can be calculated with the equation. A current loop generates a magnetic field all around itself as shown in picture. Vector potential and magnetic induction for a circular current loop we consider the problem of a circular loop of radius a, lying in the xy plane, centered at the origin, and carrying a current i, as shown in fig. To calculate the torque on a rectangular loop of currentcarrying wire sitting in an external magnetic field. Mathematically, here, a is a vector quantity with the magnitude equal to the area of the rectangular loop and the. Torque by magnetic field on a current carrying wire loop. Another name for a current loop is magnetic dipole.
The magnetic moment of a current loop can be defined as the product of current flowing in the loop and the area of the rectangular loop. A straight long wire carrying 4 a current is kept near the loop as shown in the figure. Motors are the most common application of magnetic force on currentcarrying wires. Lets say the magnetic field is in the plane of the loop and is parallel to two sides.
It explains how to derive the formula of the torque on a current carrying coil. Students begin to focus on the torque associated with a current carrying loop in a magnetic field. The torque on a currentcarrying loop physics libretexts. Therefore, the loop has a net torque and rotates to the position shown in b. The voltage across two 5 v batteries that are connected in series is 10v 3. This physics video tutorial explains how to calculate the torque on a current loop in a uniform magnetic field as well as the magnetic dipole moment. Note that the perpendicular to the loop makes an angle.
Torque causes an object to spin around a fixed axis. A current carrying loop of wire attached to a vertically rotating shaft feels magnetic forces that produce a clockwise torque as viewed from above. Jan 23, 20 so, i suppose many comforts of modern life depend on this interaction. A nonuniform magnetic field can produce a net force, but it is more complex and we will not study it in this course here we will look at the torque on the. This equation can be shown to be valid for a loop of any shape. Force on a square loop of current in a uniform bfield. The torque on a current loop boston university physics. Dec 20, 2017 this physics video tutorial explains how to calculate the torque on a current loop in a uniform magnetic field as well as the magnetic dipole moment. In addition, students learn to calculate the energy of this loop in the magnetic field. May 19, 2015 as u know torque is given by ni a x b where n and i are number of loop turns and current magnitude respectively, a is area in vector and b is magnetic field in vector. Torque on a current carrying coil in a magnetic field. Bottom side up, top side down rhr rotates around horizontal axis i.