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. How to find the torque on a current loop in a magnetic field 1. In addition, students learn to calculate the energy of this loop in the magnetic field. It explains how to derive the formula of the torque on a current carrying coil. The direction of a is perpendicular to the loop, in the direction given by the \ loop rhr. Force and torque on a current loop physics libretexts. Oct 31, 2019 free pdf download of cbse physics multiple choice questions for class 12 with answers chapter 4 moving charges and magnetism. 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. Motors are the most common application of magnetic force on current carrying wires. To start with the magnetic force on a moving charge q and derive the force on a wire segment carrying current i. 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. Each loop of current has a direction associated with it.
Torque causes an object to spin around a fixed axis. Jul 09, 2017 torque on a current carrying loop cross product of dipole moment vector and magnetic field vector magnetic moment of loopi. Force on a square loop of current in a uniform bfield. 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. 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 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. This is ia, where iis the current and the magnitude of a is the area aenclosed by the loop. The magnitude of the torque can be given by, torque on current loop the magnetic moment. So, i suppose many comforts of modern life depend on this interaction. If there is another magnet magnetic field below it the south pole at a will be attracted or repelled straight up or straight do. Amperes law solenoid material magnetism which of the following is wrong. 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. Describe how motors and meters work in terms of torque on a current loop.
Torque on a current carrying coil in a magnetic field. What is the general proof that the torque acting on an. 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. If the loop and the wire are coplanar, find i the torque acting on the loop and ii the magnitude and direction of the force on the loop due to the current carrying wire. 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. A straight long wire carrying 4 a current is kept near the loop as shown in the figure.
Bottom side up, top side down rhr rotates around horizontal axis i. Force and torque on a current loop university physics. Motors and meters openstax this work is produced by openstaxcnx and licensed under the creative commons attribution license 3. F the attempt at a solution i found out the dipole moment of the whole disc by integration,through the following method. Similarly on the side da,no magnetic force acts since current element makes an angle. 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. Therefore, the loop has a net torque and rotates to the position shown in b. Top views of a current carrying loop in a magnetic field. Jan 23, 20 so, i suppose many comforts of modern life depend on this interaction. Motors are the most common application of magnetic force on currentcarrying wires. The torque on a current loop boston university physics. 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.
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. Students begin to focus on the torque associated with a current carrying loop in a magnetic field. To calculate the torque on a rectangular loop of currentcarrying wire sitting in an external magnetic field. A current loop generates a magnetic field all around itself as shown in picture. Torque on currentcarrying loop in magnetic field motor theory. Torque on current carrying loopdiploe moment of loop. Lets say the magnetic field is in the plane of the loop and is parallel to two sides. A, i is current in the loop,a is its area and of course, torque at a pointr. The torque on a currentcarrying loop physics libretexts. Now we shall show that a steady current i passing through a rectangular loop placed in a uniform magnetic field. If the coil having n rectangular loop is placed in magnetic field then torque is given by. Clicker 1 torque on a current loop university of florida.
Calculate the magnetic field magnetic field induced at the center of a loop loop or coil coil or at the interior of a solenoid. Calculate the torque on a currentcarrying loop in a magnetic eld. What happens when we place a rectangular loop carrying a current i in the xy plane and switch on a uniform magnetic field. No magnetic forces act on sides 1 and 3 because these wires are parallel to the. 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. 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 carrying loop of wire attached to a vertically rotating shaft feels magnetic forces that produce a clockwise torque as viewed from above. Another name for a current loop is magnetic dipole. Torque by magnetic field on a current carrying wire loop. Calculate the magnetic torque magnetic torque on a coil or solenoid of area a, turns n, and current i in a given bfield. 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. A currentcarrying loop of wire attached to a vertically rotating shaft feels magnetic forces that produce a clockwise torque as viewed from above. Physics mcqs for class 12 chapter wise with answers pdf download was prepared based on latest exam pattern. Torque on a current loop, electrical motor magnetic field around a current carrying wire. 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. Calculate the torque on a current carrying loop in a magnetic field. Magnetic force, torque, and magnetic moments objectives 1. Magnetostatics university of colorado colorado springs.
Torque on current loop iconsider rectangular current loop forces in left, right branches 0 forces in topbottom branches cancel no net force. Torque on a current carrying rectangular loop in a magnetic. This is the torque on a current carrying loop in a uniform magnetic field. Through the associated activity, get your motor running, students explore a physical model to gain empirical data and. Torque on current loop and magnetic moment derivation with. Physics mcqs for class 12 with answers chapter 4 moving. Note that the perpendicular to the loop makes an angle. 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. Apparatus horseshoe magnet or pair of bar magnets, loop of wire attached to power supply. 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.
Forcetorque on a current loop due to its own magnetic field. 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. Torque on currentcarrying loop in magnetic field motor. How to find the torque on a current loop in a magnetic field. Torque on current carrying loop definition, examples, diagrams. 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. 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. Magnetic torques and amps law a magnetic field exerts a force on a straight wire carrying current. Students can solve ncert class 12 physics moving charges and magnetism mcqs pdf with answers to know their.
The voltage across two 5 v batteries that are connected in series is 10v 3. A uniform magnetic field exerts no net force on a current loop but it does exert a net torque. Magnetic torques and amps law rochester institute of. This equation can be shown to be valid for a loop of any shape. Mathematically, here, a is a vector quantity with the magnitude equal to the area of the rectangular loop and the. 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. The loop carries a current, has turns, each of area, and the perpendicular to the loop makes an angle with the field. The torque exerted by the magnetic force including both sides of the coil is given by. What is the magnitude of the torque on the circular current loop in the figure.