This document discusses magnetic fields and their properties. It explains that magnets have two poles, north and south, and that like poles repel while unlike poles attract. It defines magnetic fields as representing magnetic forces that act at a distance without physical contact. It describes magnetic field lines and their properties, including that their direction shows the field orientation and strength increases with closer spacing. It discusses the force on moving charges in magnetic fields, including how this causes circular or spiral motion, and explains the Hall effect where a magnetic field perpendicular to current flow in a conductor creates a voltage across it.
basic principles of electrical machines,faraday's laws of electro magnetic induction principle.dynamically induced Emf statically induced emf applications to electrical machines
basic principles of electrical machines,faraday's laws of electro magnetic induction principle.dynamically induced Emf statically induced emf applications to electrical machines
An electromagnet is a magnet that runs on electricity. Unlike a permanent magnet, the strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. ... An electromagnet works because an electric current produces a magnetic field. Electromagnetism is produced when an electrical current flows through a simple conductor such as a length of wire or cable, and as current passes along the whole of the conductor then a magnetic field is created along the whole of the conductor.
This is first PPT in the electrostatics series. This PPT presents idea of charge , its various methods of production like through conduction, friction, induction. It also describes working of electroscope & concept of grounding of an insulator.
An electromagnet is a magnet that runs on electricity. Unlike a permanent magnet, the strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. ... An electromagnet works because an electric current produces a magnetic field. Electromagnetism is produced when an electrical current flows through a simple conductor such as a length of wire or cable, and as current passes along the whole of the conductor then a magnetic field is created along the whole of the conductor.
This is first PPT in the electrostatics series. This PPT presents idea of charge , its various methods of production like through conduction, friction, induction. It also describes working of electroscope & concept of grounding of an insulator.
Useful in the coarse of energy conversion for computer engineering students.
coverage: history of magnetism, Right hand rule, force due to magnetic field, motor and generator, Electromagnetic of straight conductor, loops, solenoid, magnetic dipole moment, materials of magnetism, faradays law of magnetism,
Contents
Magnets, Ferromagnets and Electromagnets
Magnetic Fields and Magnetic Field Lines
Magnetic Field Strength: Force on a Moving Charge in a Magnetic Field
The Hall Effect
Magnetic Force on a Current-Carrying Conductor
Torque on a Current Loop: Motors and Meters
Magngetic Fields Produced by Currents: Ampere‘s Law
Magnetic Force between Two Parallel Conductors
Describe the difference between the north and south poles of a magnet.
Describe how magnetic poles interact with each other.
Define Ferromagnet.
Describe the role of magnetic domain in magnetization.
Describe the relationship between electricity and magnetism.
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Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
2. Magnets
All magnets attract iron, such as that in a refrigerator door. However, magnets may
attract or repel other magnets.
Experimentation shows that all magnets have two poles. If freely suspended, one
pole will point toward the north.
The two poles are thus named the north magnetic pole and the south magnetic
pole.
It is a universal characteristic of all magnets that like poles repel and unlike
poles attract.
3. Magnetic Fields
Einstein is said to have been fascinated by a compass as a child, perhaps musing
on how the needle felt a force without direct physical contact.
His ability to think deeply and clearly about action at a distance, particularly for
gravitational, electric, and magnetic forces, later enabled him to create his
revolutionary theory of relativity.
Since magnetic forces act at a distance, we define a magnetic field to represent
magnetic forces.
4. Magnetic Fields
The pictorial representation of magnetic field lines is very useful in visualizing the
strength and direction of the magnetic field.
The direction of magnetic field lines is defined to be the direction in which the
north end of a compass needle points. The magnetic field is traditionally called the
B-field.
A field is a way of mapping forces surrounding any object that can act on another
object at a distance without apparent physical connection. The field represents the
object generating it. Gravitational fields map gravitational forces, electric fields map
electrical forces, and magnetic fields map magnetic forces.
5. Properties of magnetic field lines
1. The direction of the magnetic field is tangent to the field line at any point in space.
A small compass will point in the direction of the field line.
2. The strength of the field is proportional to the closeness of the lines. It is exactly
proportional to the number of lines per unit area perpendicular to the lines (called
the areal density).
3. Magnetic field lines can never cross, meaning that the field is unique at any point
in space.
4. Magnetic field lines are continuous, forming closed loops without beginning or end.
They go from the north pole to the south pole.
6. Force on a Moving Charge in a
Magnetic Field
What is the mechanism by which one magnet exerts a force on another? The
answer is related to the fact that all magnetism is caused by current, the flow of
charge.
Magnetic fields exert forces on moving charges, and so they exert forces on other
magnets, all of which have moving charges.
7. Right Hand Rule
The magnetic force on a moving charge is one of the most fundamental known.
Magnetic force is as important as the electrostatic or Coulomb force.
Yet the magnetic force is more complex, in both the number of factors that affects it
and in its direction, than the relatively simple Coulomb force.
Themagnitude of the magnetic force F on a charge q moving at a speed v in a
magnetic field of strength B is given by
𝐹 = 𝑞𝑣𝐵 sin 𝜃
8. Right Hand Rule
where θ is the angle between the directions of v and B.
This force is often called the Lorentz force. In fact, this
is how we define the magnetic field strength B —in terms
of the force on a charged particle moving in a magnetic
field.
The SI unit for magnetic field strength B is called the
tesla (T)
𝐵 =
𝐹
𝑞𝑣 sin 𝜃
The direction of the magnetic force F is perpendicular to
the plane formed by v and B , as determined by the
right hand rule.
9. Force on a Moving Charge in a
Magnetic Field
Magnetic force can cause a charged particle to move in a circular or spiral path.
Cosmic rays are energetic charged particles in outer space, some of which
approach the Earth. They can be forced into spiral paths by the Earth’s magnetic
field.
Protons in giant accelerators are kept in a circular path by magnetic force.
The curved paths of charged particles in magnetic fields are the basis of a number
of phenomena and can even be used analytically, such as in a mass spectrometer.
10. Force on a Moving Charge in a
Magnetic Field
So does the magnetic force cause circular motion?
Magnetic force is always perpendicular to velocity, so that it does no work on the
charged particle.
The particle’s kinetic energy and speed thus remain constant.
The direction of motion is affected, but not the speed.
This is typical of uniform circular motion.
The magnetic force supplies the centripetal force
𝐹𝑐 =
𝑚𝑣2
𝑟
Noting that sin θ = 1 , we see that F = qvB
11. A negatively charged particle
moves in the plane of the page in
a region where the magnetic field
is perpendicular into the page
The magnetic force is
perpendicular to the velocity, and
so velocity changes in direction
but not magnitude. Uniform
circular motion results.
12. Force on a Moving Charge in a
Magnetic Field
𝑞𝑣𝐵 =
𝑚𝑣2
𝑟
𝑟 =
𝑚𝑣
𝑞𝐵
Here, r is the radius of curvature of the path of a charged particle with mass m and
charge q , moving at a speed v perpendicular to a magnetic field of strength B .
If the velocity is not perpendicular to the magnetic field, then v is the component of
the velocity perpendicular to the field.
Thecomponent of the velocity parallel to the field is unaffected, since the magnetic
force is zero for motion parallel to the field.
This produces a spiral motion rather than a circular one.
13. The Hall Effect
We have seen effects of a magnetic field on free-moving charges. The magnetic
field also affects charges moving in a conductor. One result is the Hall effect,
14. The Hall effect
The field is perpendicular to the electron drift velocity and to the width of the
conductor.
Note that conventional current is to the right in both parts of the figure. In part
(a), electrons carry the current and move to the left.
(b), positive charges carry the current and move to the right.
Moving electrons feel a magnetic force toward one side of the conductor, leaving a
net positive charge on the other side. This separation of charge creates a voltage ε
, known as the Hall emf, across the conductor.
The creation of a voltage across a current carrying conductor by a magnetic field is
known as the Hall effect,
15.
16. Numerical
A Hall effect flow probe is placed on an artery, applying a
0.100-T magnetic field across it. What is the Hall emf,
given the vessel’s inside diameter is 4.00 mm and the
average blood velocity is 20.0 cm/s?