Electrostatics/Magnetism Flashcards
Electrostatic force
F = kq1q2/r^2 (coulomb’s law)
Measures force between two charges that are a certain distance apart.
Both objects experiences the same magnitude of force from one another.
Force is inverse and squared to distance between charges.
If r increases by a factor of 7, F decreases by a factor of 49.
If r increases by a factor of 2, F decreases by a factor of 4..
Electrostatic potential energy
U = F x distance
U = kq1q2/r
delta U = q delta V
Potential energy between two charges - work required to move one charge into the electric field of another charge.
If charges are like, U is +, if charge are opposite, U is -
If charge is further away, it has more potential energy.
Electrostatic potential
V = U/q
V = kq1/r
ratio of the magnitude of electrical potential energy of a charge to the magnitude of a charge.
Inversely proportional to distance between charge and source charge (r increases and V decreases)
(-) test charge moves from low -> high electrical potential, (+) test charge spontaneously moves from high -> low electrical potential
Electric field
E = kq1/r^2
E = F/q
units: N/C
Measures the magnitude of the electric field created by a source charge by measuring the force exerted at a point in space, or relative to a test charge.
Vector quantity b/c + charge has electric field direction pointing away from itself, while a - charge has field lines pointing towards itself - tells us the direction of a + charge when exposed to the field.
charging by induction
polarization (separation of charges by applying another charged object) followed by conduction (electrons exit object.)
Leaves the object with a net charge that is opposite of the polarizing object.
What is polarization?
Which types of materials can be polarized?
+ and - charges in an object separate when contacted by a + or - charged object.
Occurs with conductors and insulators.
How do you return a conductor’s overall charge back to neutral?
touch with another neutral conductor
What does a higher density of electric field lines indicate?
stronger charge
Magnetic field - units/relationships
units: T (tessla) = Ns/mC = N/Am
B is proportional to the current (flow of + charge), and inversely proportional to the distance from the charge.
How do you determine the direction of a charge interacting with the magnetic field around a current-carrying wire?
use the right hand rule - thumb points in direction of current, fingers curl around in the direction of the magnetic field, palm points in direction of force.
What is required of a charge for it to be affected by a magnetic field? electric fields?
It must be moving for a magnetic charge to affect it.
An electric field moves any moving or non-moving charge.
Magnetic force on a moving charge
F = qVBsin(theta)
If theta is 90, a force will be exerted. If theta is 0 or 180, F =0 (magnetic field will exert a force 90 from direction of charge)
Centripital force = ?
Fc = mv^2/r = qVB
