Ch 26: Magnetic Fields and ForcesSee all chapters
All Chapters
Ch 01: Units & Vectors
Ch 02: 1D Motion (Kinematics)
Ch 03: 2D Motion (Projectile Motion)
Ch 04: Intro to Forces (Dynamics)
Ch 05: Friction, Inclines, Systems
Ch 06: Centripetal Forces & Gravitation
Ch 07: Work & Energy
Ch 08: Conservation of Energy
Ch 09: Momentum & Impulse
Ch 10: Rotational Kinematics
Ch 11: Rotational Inertia & Energy
Ch 12: Torque & Rotational Dynamics
Ch 13: Rotational Equilibrium
Ch 14: Angular Momentum
Ch 15: Periodic Motion (NEW)
Ch 15: Periodic Motion (Oscillations)
Ch 16: Waves & Sound
Ch 17: Fluid Mechanics
Ch 18: Heat and Temperature
Ch 19: Kinetic Theory of Ideal Gasses
Ch 20: The First Law of Thermodynamics
Ch 21: The Second Law of Thermodynamics
Ch 22: Electric Force & Field; Gauss' Law
Ch 23: Electric Potential
Ch 24: Capacitors & Dielectrics
Ch 25: Resistors & DC Circuits
Ch 26: Magnetic Fields and Forces
Ch 27: Sources of Magnetic Field
Ch 28: Induction and Inductance
Ch 29: Alternating Current
Ch 30: Electromagnetic Waves
Ch 31: Geometric Optics
Ch 32: Wave Optics
Ch 34: Special Relativity
Ch 35: Particle-Wave Duality
Ch 36: Atomic Structure
Ch 37: Nuclear Physics
Ch 38: Quantum Mechanics

Concept #1: Magnetic Force on Current-Carrying Wire

Example #1: Find Force on Current-Carrying Wire at an Angle

Practice: A 5-m current-carrying wire (red line) is ran through a 4 T magnetic field (blue lines), as shown. The angle shown is 30°. What must the magnitude and direction of the current in the wire be when it feels a 3 N force directed into the page?

Additional Problems
A 1m, straight wire carrying a 1.5 mA current in the presence of a perpendicular, 2mT magnetic field will feel a force due to that magnetic field. Because of this force, the wire should deform, as shown in the following figure. However, this deformation causes stretching in the wire (obviously the arc is a further distance than 1m), and if the wire is elastic, then there will be some elastic force that resists stretching. If we can treat the wire like we treat a spring, and say the elastic force is proportional to the vertical displacement, Fel = -kΔy, how much could the wire stretch if k = 300 N/m? Assume that the wire is still essentially 1m long after stretching.
A straight segment of wire is in a region of uniform magnetic field. If the current in the wire is toward the right and the direction of the magnetic field is into the page, as shown in the sketch, the direction of the force on the wire is A) into the page B) out of the page C) to the left D) to the right E) toward the top of the page F) toward the bottom of the page
A long wire carrying 4.50 A of current makes two 90° bends, as shown in the figure. The bent part of the wire passes through a uniform 0.500 T magnetic field directed as shown in the figure and confined to a limited region of space. What is the magnitude of the net force acting on the wire?
A straight wire segment carries current towards the left in a magnetic field that is directed into the page. What is the direction of the force that the magnetic field exerts on the wire? (a) to the left (b) to the right (c) toward the top of the page (d) toward the bottom of the page (e) into the page (f) out of the page
A wire that is lying in the plane of the page carries current  I in the direction toward the top of the page, as shown in the sketch. The wire is in a uniform magnetic field (produced by a large electromagnet) that is directed into the page. The direction of the force that the magnetic field exerts on the wire is A) toward the top of the page B) toward the bottom of the page C) to the right D) to the left E) out of the page F) into the page G) no direction since the force is zero
A 5 meter length of wire carrying a current of 5 A lies on a horizontal table with a rectangular top of dimensions 0.300 m × 0.400 m. The ends of the wire are attached to opposite ends of a diagonal of the rectangle. A vertical magnetic field of 0.30 T is present. What magnetic force acts on this segment of wire?  A) 1.1 N B) zero C) 7.5 N D) 0.75 N E) The force cannot be determined without knowing the shape of the length of wire.
A wire in the shape of an "M" lies in the plane of the paper. It carries a current of 2.0 A, flowing from A to E. It is placed in a uniform magnetic field of 0.65 T in the same plane, directed as shown in Figure 1. What is the magnitude and direction of the force acting on section BC of this wire? A) 0.090 N perpendicular into the page B) 0.060 N perpendicular out of the page C) 0 N D) 0.090 N perpendicular out of the page E) none of the above