physics w

• Magnetism


  Deals with the study of the source and nature of magnetism, the behavior of material with the presences of magnetic field, and magnetic force

  
• Magnesia


  The origin of the word "magnetism"
• Two branches of magnetism

  • Magnetostatics "magnetic source at rest"
  • Magnetodynamics "source of magnetism is in motion"

  
• Magnet


  • Any material that has ability to attract metal
  • Can be permanent or temporary
  • Alignment of atoms is called magnetic domains
  • Has two poles, a north pole (N) and a south pole (S)
  • Law of magnetic poles: unlike attracts, like repels
  • Magnetic poles always occur in pairs of north and south

  
• Dipole


  A magnetic system with two poles of opposite magnetic polarity
• Monopole


  A theoretical concept in magnetism that represents a single magnetic pole, either a north pole or a south pole, existing without its opposite counterpart

  
• Paul Dirac, a British theoretical physicist, proposed the idea of magnetic monopoles in 1931
• Types of magnets


  • Ferromagnetic Materials: Strongly attracted to magnets and can be magnetized, including iron, nickel, cobalt, and alloys
  • Diamagnetic Materials: Weakly repelled by magnets, lose magnetism when the magnetic field is removed, examples are copper or silver
  • Paramagnetic Materials: Weakly attracted to magnets, retaining some magnetization even after the magnetic field is removed, like aluminum or oxygen
• Types of magnets


  • Electromagnets: Generated by electric current through wire coils, allowing control of magnetism, used in devices like motors or MRI machines
  • Superconducting Magnets: Generated by superconducting materials at low temperatures, producing strong magnetic fields, utilized in MRI machines, particle accelerators, or maglev trains

  
• Magnetic field


  A region around a magnet in which magnetic effects are observed

  
• Magnetic fields are created by moving electric charge

  
• Calculating the magnitude and direction of the magnetic field 2cm to the right of a vertical wire carrying a current of 45A due south

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• Lorentz force


  The force exerted on a charged particle q moving with velocity v through an electric field E and magnetic field B

  
• The magnetic force is orthogonal to the magnetic field

  
• Calculating the magnitude and direction of the resulting force on a 2-nC charge projected to the east with velocity 5 x 10^4 m/s at an angle of 30° with a 3T magnetic field

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• Finding the magnitude of the magnetic field that will cause an electron at point A to follow a semicircular path from A to B

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• Calculating the magnitude of the magnetic force on a 2.5m long wire carrying a current of 5.0A in the presence of a magnetic field with a strength of 2.0 × 10^-3 T

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• Magnetic flux


  The total number of field lines entering in a given area

  
• The magnetic flux through any closed surface is zero (Gauss's law for magnetism)

  
• Calculating the magnitude of magnetic flux in a square of side 3.0 cm placed in a 0.004 T magnet at an angle of 20° relative to the magnetic field

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• Faraday's Law of electromagnetic Induction

  Describes how a changing magnetic field induces an electromotive force (emf) in a closed circuit

  
• Voltage


  A measure of the electric potential difference between two points in an electrical circuit, representing the energy per unit charge required to move a charge between those points
• Electromotive force (emf)


  The total energy per unit charge supplied by a source, such as a battery or a generator, to drive electric current through a circuit
• Faraday's experiments with magnets and coils of wire demonstrated the link between magnetism and electricity

  
• Lenz's Law


  Any change in magnetic flux through a closed loop induces an electromotive force (emf) in the loop, resulting in an induced current that generates a magnetic field opposing the change in flux

  
• Factors that influence voltage production

  • Number of coils
  • Changing magnetic field
• According to Faraday's law, only changes in magnetic flux matter, rapid changes in magnetic flux produce larger values of electromotive force than do slow changes, the magnitude of the electromotive force is proportional to the rate of change of the flux, and the induced emf is present even if there is no current in the path enclosing an area of changing magnetic flux

  
• Induction


  The magnetic field which is proportional to the rate of change of the magnetic field

  
• Inductance


  The electromotive force generated to oppose the change in current at a particular time duration
• Calculating the approximate value of the emf induced in a wire loop of area 1 cm2 when a strong bar magnet with B =1 T is suddenly inserted into the loop in 0.1 s

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• Calculating (a) the induced emf in a square coil (20cm x 20cm) of 50 loops with a magnetic field perpendicular to the face of the coil increasing from -3T to 5T in 0.10 seconds, and (b) the current flowing through a 20 ohm resistor connected across the coil

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• Types of electricity


  • Static Electricity
  • Current Electricity
• Direct Current (DC)


  The current flows in one direction continuously without changing polarity over time, with DC voltage and current remaining constant over time
• Alternating Current (AC)


  The direction of current flow alternates periodically, with AC voltage and current typically following a sinusoidal waveform

  
• Electromagnetic Waves


  A changing magnetic flux produces an induced emf (electromotive force), which is always associated with an electric field. A changing magnetic field produces an electric field.

  
• The direction of the induced electric field is perpendicular to the magnetic field that produced it, and the magnetic field produced by a changing electric field is perpendicular to the electric field that produced it.

  
• In an electromagnetic wave, the electric field and magnetic fields are perpendicular to each other, and the direction of propagation of the wave is perpendicular to both the electric field and magnetic field.

  
• James Clerk Maxwell formulated the theory of electromagnetism, which is encapsulated in Maxwell's equations.
• Electromagnetic Waves (EM waves)


  Composed of oscillating magnetic and electric fields, forming when an electric field comes in contact with a magnetic field.

  
• EM waves travel with a constant speed of 299,792,458 m/s, can interfere and diffract, and can travel through anything including air, solid materials, and vacuum.