7.4 Magnetic fields

• What is a magnetic field?

  Region with magnetic force
• In which direction do magnetic field lines flow outside a magnet?

  North to South
• What is the value of the permeability of free space in SI units?

  $4\pi \times 10^{ - 7} \, \text{T m / A}$
• What is magnetic flux density measured in?

  Tesla (T)
• What is the symbol for magnetic flux?

  $\Phi$
• Magnetic flux density is a vector quantity measured in Tesla (T).

  True
• What is a magnetic field?

  Region with magnetic force
• What is the direction of magnetic field lines outside a magnet?

  North to South
• The permeability of free space, denoted as $\mu_{0}$, has a value of $4\pi \times 10^{ - 7}$ T m / A.free
• Magnetic flux density is the magnetic flux per unit area.


  True
• The direction of the magnetic force on a moving charged particle in a magnetic field is determined by the right-hand rule.
• What is the formula for the magnetic force on a charged particle moving in a magnetic field?

  $F =$$qvB \sin \theta$
• Steps to determine the magnetic force using the right-hand rule

  1️⃣ Curl the fingers in the direction of the magnetic field

  2️⃣ Point the thumb
• Induced emf can cause an induced current if the circuit is open.

  False
• In MRI, strong magnetic fields align the magnetic moments of hydrogen nuclei
• The strength of a magnetic field is measured in Tesla
• The magnetic field strength around a long straight wire is given by B = \frac{\mu_{0} I}{2\pi r}</latex>, where $\mu_{0}$ is the permeability of free space
• Permanent magnets generate magnetic fields due to the alignment of atomic magnetic dipoles
• The formula for magnetic flux is $\Phi =$$BA$, where $A$ is the area
• What is the symbol for magnetic flux density?

  $B$
• In the formula $\Phi =$$BA$, $A$ represents the area
• Match the property of a magnetic field with its description:

  Source ↔️ Magnets, moving electric charges

  Nature ↔️ Vector field

  Direction ↔️ North to South outside magnet
• What is the formula for magnetic field strength around a long straight wire?

  $B =$$\frac{\mu_{0} I}{2\pi r}$
• Electric currents create a magnetic field due to the movement of charges
• Match the quantity with its formula and unit:

  Magnetic Flux ↔️ \Phi = BA</latex> ||| Weber (Wb)

  Magnetic Flux Density ↔️ $B =$$\frac{\Phi}{A}$ ||| Tesla (T)
• What is the formula for the magnetic force on a charged particle in a magnetic field?

  $F =$$qvB \sin \theta$
• The magnitude of the magnetic force on a charged particle is directly proportional to its charge
• Faraday's Law states that the induced emf is equal to the negative rate of change of magnetic flux
• Match the application with its use of magnetic fields:

  Electric Motors and Generators ↔️ Convert electrical and mechanical energy

  Particle Accelerators ↔️ Accelerate charged particles

  Magnetic Resonance Imaging (MRI) ↔️ Produce detailed body images

  Magnetic Data Storage ↔️ Store data on hard disks

  Magnetic Levitation (Maglev) Trains ↔️ Propel trains at high speeds
• A magnetic field is a scalar field.

  False
• Magnetic field strength is inversely proportional to current in a wire.

  False
• What are the two sources of magnetic fields mentioned in the study material?

  Permanent magnets, electric currents
• Magnetic flux density is a scalar quantity.

  False
• Magnetic flux is a scalar quantity measured in Weber
• What is the formula relating magnetic flux and magnetic flux density?

  $\Phi =$$BA$
• A magnetic field is a vector field with both magnitude and direction.


  True
• Magnetic field strength is directly proportional to current in a wire.


  True
• What is the origin of magnetic fields in permanent magnets?

  Alignment of atomic dipoles
• What is the unit of magnetic flux?

  Weber (Wb)
• What are the three factors that influence the magnitude of the magnetic force on a charged particle?

  Charge, velocity, field strength