Describe the direction of the magnetic force action on a current-carrying wire in a uniform magnetic field
the direction is perpendicular to the direction of the field and the current
When is the magnetic force the strongest on a current-carrying wire in a uniform magnetic field?
when the current is perpendicular to the magnetic field lines
The magnitude of the magnetic field at a certain distance from a long, straight conductor is represented by B. What is the magnitude of the magnetic field at twice the distance from the conductor?
magnitude= B/2
A long, straight, vertical wire carried a current upward. Due east of this wire, in what direction dies the magnetic field point?
North
Two long parallel wires are placed side by side on a horizontal tab. The wires carry equal currents in the same direction. Describe the magnetic force between them?
The magnetic force is attractive
Two long parallel wires are placed side by side on a horizontal tab. The wires carry equal currents in the same direction. What is the magnetic field at a point midway between the two wires?
0.zero
Which end of a compass needle is a north pole?
The end that points towards the north
If you place a compass near the north pole of a magnet,
what happens to the compass needle?
The north-pointing end of the needle rotates as far away
as possible from the north pole of the magnet.
Is the Earth's geographic North Pole a magnetic
north pole?
Yes
Magnetic Field lines
Tangent to the lines at every field point
Useful to represent for visually representing the strength and the direction of the magnitude
unit for magnetic force
tesla
magnetic force: when velocity is parallel to the magnitude
F =0
magnetic force: when velocity is perpendicular to the magnitude
F = qvB
magnetic force: at any given angle
F = qvBsin(x)
cross products and determinants
|uxv|=|u||v|sin(x)
what is a cyclotron?
It makes use of the magnetic force on a moving charge to bend moving charges into a semicircular path between accelerations by an applied electric field
charge moving in a uniform magnetic field
the velocity changes its direction, but not the magnitude
characteristics of a circular trajectory/a cyclotron (charge moving in a uniform magnetic field)
The magnitude of the velocity is constant
The force is always perpendicular to the velocity
Particles trapped in magnetic field lines
the magnetic force on a moving particle is always perpendicular to the motion, as well as to the magnetic field lines.
when particles are trapped in magnetic field lines what is not affected by the magnetic force?
motion that is not parallel to the field
velocity vector and magnetic field lines are perpendicular
causes the object to moving a circular motion
Cyclotron
velocity vector and magnetic field lines are parallel
their magnetic force acting on them is 0 (cross product)
velocity vector and magnetic field lines are nor parallel or perpendicular
- x-component: will move in the circular motion because it is perpendicular to the magnetic field lines
- y-component: will experience nothing because it is parallel to the magnetic field lines
- if the charge is positive: counter-clockwise
- negative: cl
magnetic field on a current
force is perpendicular to both the current and the magnetic field
the direction doesn't depend on the sign of the charge
hall effect
The separation of charges across a current-carrying wire
potential difference: hall potential
what does the direction of the electric field and the sign of potential difference depend on?
the sign of the charge carriers
Bio-Savart Law
It gives the magnitude field of a charged particle moving with a velocity
Def: it is the relationship between the magnetic field contribution and its source current element
magnetic force between conductors (assuming parallel)
The magnetic force between parallel currents in the same direction is attractive
Anti-parallel currents: reversing one of the currents would change the sign of both forces = repulsion
magnetic dipole moment
The strength of a magnetic dipole
A vector quantity with direction perpendicular to the current loop
Magnetic dipole moment: N-turn current loop
when practical loops have multiple turns and since each carries the same current, an N-turn loop has effective current NI
differences and similarities between electric dipole and magnetic dipole
Electric: origin in static electric charge
Magnetic: origin in moving charge (charge moving in a closed loop)
Similarities: same field configuration and mathematical form. They are both characterized by their respective dipole moments
current loop field
more concentrated in the center/inside
as you move away from the center, both the magnitude and direction change
torque on a magnetic dipole
Causes the magnetic dipole moment with the magnetic field
Causes magnetic dipoles (current loops) to align with their dipole moment vectors along the magnetic field
what happens to the torque on the magnetic dipole when the field is non-uniform?
experiences a net force
inherent magnetic field in electrons
- electrons aligned with the magnetic field =+1/2
- vice versa: -1/2
Ferromagnetism
characteristic of elements such as iron, nickel, and cobalt in which the magnetic domains are aligned
paramagnetism
Magnetism caused when the atomic dipoles align with an external field
Attraction to magnetic field caused by unpaired electron
dimagnetism
all the electrons are paired so magnetism cant affect it
Gauss's law of electric field
The electric flux over any surface is proportional to the charge enclosed by that surface
Magnetic flux emerging from any enclosed surface is
always 0
Ampere's Law
States that for any closed loop path , the sum of the length elements times the magnetic field in the direction of the length is equal to the permeability times the electric current enclosed in the loop.
Provides a global description of the magnetic field
Line integrals:
perpendicular
tangent
If magnetic field is perpendicular everywhere to a line = 0
If magnetic field(B) is tangent everywhere to a line of length (l) AND has the same magnitude at every point = Bl
Solenoid Field
solenoid: a tightly wound coil
since the rectangle's vertical dimension never entered the calculation= the field has the same magnitude everywhere inside the solenoid
induced current
magnetic field must change to produce an electric current
electromagnetic induction
the process of creating a current in a circuit by changing a magnetic field