Chapter 7: Magnetisim Flashcards
The two necessary conditions for the generation of magnetic fields are:
charge and movement of that charge
The SI unit of the magnetic field is the:
Tesla (1 T = 1 Ns/mC)
Small magnetic fields are sometimes measured in:
gauss
1 Tesla is equivalent to how many gauss?
104 (1 gauss = 1 X 10-4 T)
Diamagnetic materials are:
weakly antimagnetic materials in which all electrons are paired; “non-magnetic”
Paramagnetic materials are:
materials that possess some unpaired electrons and become weakly magnetic in an external magnetic field
Ferromagnetic materials are:
strongly magnetic materials that possess some unpaired electrons with atoms organized in magnetic domains
Curie temperature is:
the temperature for all ferromagnetic materials above which they are paramagnetic and below which they are strongly and permanently magnetic
Magnetic field lines are:
circular
Current carrying wire generates a:
magnetic field in its vicinity. The net magnetic field of the current is equal to the vector sum of the magnetic fields of all the individual moving charges that comprise the current.
Electric current is:
the flow of charge between two points of different electric potentials connected with a conductor
Equation to determine the total electric current passing through a conductor per unit of time:
i = Δq / Δt
where i = the magnitude of the current, Δq = the amount of charge passing through the conductor, and Δt = the time
The SI unit of current is:
ampere (1 A = 1 C/s)
The direction of current, by convention, is the direction in which:
positive charge would flow from higher potential to lower potential. The direction of current is opposite to the direction of electron flow.
Equation to determine the magnitude of the magnetic field produced by a straight current-carrying wire at a chosen point in space:
B = u0i / 2πr
where B is the magnetic field at distance r from the wire, u0 is the permeability of free space (4π X 10-7 T)
The shape of the magnetic fields surrounding a current is:
concentric perpendicular circles of magnetic field vectors
To determine the direction of the field vectors in a magnetic field, use the:
First right hand rule.
1) right-hand thumb points in direction of current
2) your right fingers curl in and mimic the circular magnetic field lines that curl around the current
Equation to determine the magnitude of the magnetic field produced by a circular loop of current-carrying wire at the center of the loop:
B = u0i / 2r
where B is the magnetic field at distance r from the wire, u0 is the permeability of free space (4π X 10-7 T)
Straight current carrying wires create magnetic fields that are:
perpendicular concentric circles surrounding the wire
Circular loops of current carrying wire create magnetic fields that are:
perpendicular concentric circles surrounding the wire
Equation to determine the magnetic force on a moving charge in an external magnetic field:
F = qvBsinØ
where q is the charge, v is the velocity of the charge, B is the magnitude of the magnetic field, and Ø is the smallest angle between vector qv and the magnetic field vector B
If a charge is moving with a velocity that is parallel or antiparallel to the magnetic field vector, it will experience:
no magnetic force
To determine the direction of magnetic force on a moving charge, use the:
Second right hand rule:
1) right-hand thumb points in the direction of vector qv (positive charge in the direction of v, negative charge opposite direction of v)
2) Fingers point towards the direction of the magnetic field
3) Your palm then indicates the direction of the magnetic force vector F on the moving point charge q.
Magnetic field vectors going into the page are represented by:
X’s
Magnetic field vectors coming out of the page are represented by:
Dots
The direction of the magnetic force on a negative charge moving through a magnetic field is ___ to the direction of the magnetic force acting on a positive charge moving in the same direction.
opposite
Charges moving into a magnetic field perpendicular to the magnetic field vector will assume what kind of motion?
uniform circular motion with constant velocity; the centripetal force in the magnetic force
When a charge is moving in uniform circular motion due to an external magnetic field, a change in strength of the magnetic field will result in:
a change in the radius of the circular pathway, not a change in the magnitude of its velocity
Formula for centripetal force of a charged particle moving perpendicular to the magnetic field vector:
F = qvb = mv2/r
Equation used to determine the magnetic force on a current carrying straight wire in a uniform external magnetic field:
F = iLBsinØ
where i is the current, L is the length of the wire, and Ø is the angle between the current and the magnetic field (B)
To determine the direction of magnetic force on a current carrying wire, use the:
Third right hand rule:
1) right-hand thumb points in the direction of the current
2) Fingers point towards the direction of the magnetic field
3) Direction of your palm then indicates the direction of the magnetic field vector
A current carrying wire placed in an external magnetic field will experience a magnetic force as long as:
the current has a directional component that is not parallel or antiparallel to the magnetic field vector.
