PHYSICS FINALS

• Magnetism

  • Refers to the force applied by magnets to each other whenever their magnetic poles attract or repel
  • Result of the interactions between moving electrons in objects
• Magnetic Forces

  • Occurs when a magnetic field is produced around a moving charge or electrical current, which another charge or current interacts with.
• • In 1820, Danish physicist Hans Christian Oersted first established that moving charges cause magnetism by (accidentally) demonstrating how a wire that contains electric current could deflect a compass needle
• Magnetic Attraction

  • Occurs when two opposite magnetic poles are placed alongside each other
• Magnetic Repulsion

  • Occurs when two similar magnetic poles are beside each other
• Magnetic Nature of the Earth

  • The geographic and magnetic poles of the Earth are different
  • The Earth’s north magnetic pole is its magnetic field’s south pole
• Charges can be isolated, it can either be positive or negative
• Michael Faraday’s Magnetic Field Induction Experiment

  • This experiment proved that a changing magnetic field is required to cause a flow of current.
• Electric forces result from and interact with both stationary and moving charges
• A single electric point charge exists (monopoles)
• Electric field lines (flux lines) have fixed starting and ending points
• Magnetic forces result from and interact only with moving charges
• Magnetism always have a north and south magnetic pole (Dipole in Nature)
• Magnetic field lines behave in continuous loops
• Materials that inherently generate their own magnetic fields are called magnets.
• Magnetic Field

  The area around a particular magnet where these behaviors are observed is what is referred to as magnetic field or B-field
• A magnetic field is a vector quantity
• The direction of the magnetic fields can be determined using a compass
• Magnetometer

  • Most common devices to measure the magnitude of magnetic fields
• Field lines are drawn such that each line through any point is tangential to the magnetic field vector.
• Field lines will never intersect since the direction of the magnetic field at each point is unique and distinct.
• They do not have endpoints. These lines continue through the magnet’s interior.
• Since the lines are not directed into the force of a charge, they are not considered lines of force.
• In the case of uniform magnetic fields, magnetic poles are flat and parallel with each other.
• For electrically-charged wires, the magnetic field is better represented on paper not by lines, but by dots and crosses.
• For an electrically-charged loop or a solenoid, the magnetic field is illustrated in the form of a typical loop.
• Magnetic Flux

  • The number of magnetic field lines passing through a given surface
• • The SI unit for magnetic flux ΦB is the Weber (Wb) which is equivalent to 1 volt per second.
• Magnetic field (B) is measured in tesla (T), which is equivalent to 1 newton per second, or 1 coulomb per meter.
• A magnetic field density of 1 Wb/m2 is equivalent to 1 Tesla.
• Gauss’s Law for Magnetism

  • The magnetic flux heading inward to the south pole is equal to the magnetic flux outward, coming from the north pole
• Magnetic Force

  • Interaction between electrically-charged particles resulting from their motion
• 1. The magnitude of the magnetic force is proportional to the magnitude of the charge
• The magnitude of the magnetic force is proportional to the magnitude of the magnetic field
• The magnetic force is affected by the charged particle’s velocity
• The magnetic force is perpendicular to the field and the velocity
• Right-Hand Rule

  • Used to determine the direction of the magnetic force on a positive charge moving in a magnetic field
• • When 2 charged particles that have equal but opposite magnitudes are moving with equal velocity in the same field, the forces on the charged particles are also equal in magnitude, but opposite in direction.
• Motion of Charged Particles in a Magnetic Field

  • “Particle’s motion as influenced by the field alone may be treated with constant speed and kinetic energy”
• If charge is positive, the particle’s revolution is counterclockwise