(electro) magnetism

• What does the direction of your thumb in the right-hand rule indicate when applied to a current-carrying wire?

  • Your thumb points in the direction of the current (I) flowing through the wire.

  
• How does the right-hand rule determine the direction of the magnetic field (B) around a straight current-carrying wire?

  • Curl your fingers in the direction of the magnetic field lines, with your thumb pointing along the current.

  
• What symbol represents the current in a wire?

  $I$

  
• What symbol represents the magnetic field?

  $B$

  
• What does the right-hand rule demonstrate regarding currents and magnetic fields?

  The relationship between current direction and magnetic field direction

  
• If the current in a straight wire is flowing upwards, what is the direction of the magnetic field at a point to the right of the wire?

  • Into the plane of the paper (away from you)

  
• If the magnetic field around a straight wire points towards you, what is the direction of the current in the wire?

  • Counterclockwise around the wire

  
• What is a magnetic domain?

  A magnetic domain is a microscopic region within a magnetic material where the magnetic moments of atoms are aligned parallel to each other

  
• Why do magnetic domains usually cancel out in bulk material?

  Because the magnetic moments in randomly oriented domains cancel each other out

  
• What happens to the magnetic domains in bulk material?

  • Domains are randomly oriented
  • Approximately half point one way
  • Approximately half point the opposite way
  • Net magnetization is zero

  
• What effect does an externally applied magnetic field have on magnetic domains?

  It aligns the magnetic domains along its direction, causing the material to become magnetized

  
• What is the state of bulk material in terms of magnetization?

  It is unmagnetized

  
• What are the three fundamental quantities involved in electromagnetic interactions?

  • Field
  • Current
  • Motion or Thrust

  
• If a current of 2 amps flows through a conductor in a 1 Tesla magnetic field, and the conductor is 0.5 meters long, what is the approximate magnitude of the force on the conductor?

  Approximately 1 Newton

  
• What is the device shown in the image?

  A solenoid

  
• What type of magnetic field is produced by a solenoid?

  A uniform magnetic field

  
• How does the magnetic field of a solenoid differ from that of a single straight wire?

  The solenoid produces a uniform magnetic field inside while a single straight wire produces a circular magnetic field.

  
• What factors determine the magnetic field strength of a solenoid?

  • Number of turns ($N$)
  • Current ($I$)
  • Length ($l$)
  • Permeability of the core material ($\mu$)

  
  

  $B = \mu \frac{N I}{l}$

  
• How does increasing the current affect the magnetic field of a solenoid?

  Increasing the current ($I$) directly increases the magnetic field strength ($B$) of the solenoid, assuming other factors remain constant.

  
• How does increasing the number of turns affect the magnetic field of a solenoid?

  Increasing the number of turns ($N$) directly increases the magnetic field strength ($B$) of the solenoid, assuming other factors remain constant.

  
• How does changing the length of a solenoid affect its magnetic field?

  Increasing the length ($l$) of the solenoid inversely affects the magnetic field strength ($B$), assuming other factors remain constant.

  
• What type of magnetic field is depicted in the image?

  Dipolar magnetic field

  
• What characterizes a dipolar magnetic field?

  • Has two poles: north and south
  • Magnetic field lines emerge from the north pole and converge at the south pole
  • Field lines form closed loops
  • Field strength is strongest near the poles and weakens with distance

  
• What tool is commonly used to visualize magnetic fields?

  Magnetic compass

  
• What is the relationship between the strength of a magnetic field and the distance from a dipole?

  The magnetic field strength weakens as the square of the distance from the dipole.

  
• What component in a speaker produces sound waves?

  Cone

  
• What is the function of the magnet in a speaker?

  Creates the magnetic field required for sound production

  
• What is the purpose of the coil in a speaker?

  Converts electrical signals into mechanical vibrations

  
• What is the basic working principle of a speaker?

  1. Electrical signals are fed into the coil
  2. Current in the coil interacts with the magnetic field from the magnet
  3. The coil and cone move according to the current
  4. The moving cone generates sound waves

  
• If the electrical signals to a speaker are increased, what would be the effect on the sound waves produced?

  The sound waves produced would be louder

  
• How does the speaker design contribute to the directionality of the sound?

  The cone shape focuses the sound waves, providing directionality

  
• What are the advantages and disadvantages of using a magnet in a speaker?

  Advantages: Provides stable magnetic field, compact Disadvantages: Heavy, requires careful handling

  
• Why is the speaker cone designed in a particular shape?

  To optimize sound directionality and efficiency

  
• Which part of the speaker is directly responsible for converting electrical energy into mechanical energy?

  Coil

  
• What are the two primary components of a DC generator?

  Permanent magnets and a current-carrying coil

  
• What role do permanent magnets play in a DC generator?

  They provide a magnetic field

  
• Why are permanent magnets essential for generating electricity?

  Because they are needed to create the magnetic flux through the rotating coil, which induces the electromotive force

  
• What type of coil is used in a DC generator?

  Current-carrying coil

  
• Why does the coil need to be current-carrying?

  Because the rotating coil must interact with the magnetic field to induce the electromotive force, which requires current flow

  
• What is the purpose of the commutator in a DC generator?

  It converts the alternating current induced in the coil into direct current