Physics - Magnetism

Chapters 27 and 28

Magnets are made of ____ materials and attract certain metals like _____

ferromagnetic materials and attract iron, nickel, cobalt, some alloys

Unlike poles ____ and like poles ___

attract, repel

The ends/faces of the magnet are the ___, and this where the magnetic effect is ____

poles, strongest

A freely suspended magnet always aligns itself in _____ direction

north-south

You _____ isolate a magnetic charge

cannot

The direction of magnetic field is _____ to a line at any point and # of lines is _____ to strength of field

tangent, proportional

Magnetic field lines always point out from _____ to ____, and form a _____

north to south, form a closed loop

Magnetic field strength ______ with distance from magnet, so field lines are ______ near the poles

decreases, stronger/denser

Earth’s magnetic field: geographic north is actually a _____
A compass needle that points north is attracted to

South pole magnet
South magnetic pole

An electric current produces a _____

Magnetic field

Magnetic field produced by current in a straight wire are in form of ____

circles

Direction of magnetic field (right hand rule) - thumb in direction of conventional current, your fingers curl in ____

direction of magnetic field lines encircling the wire with current

Strength of magnetic field is _____ to current and _____ to distance from wire

proportional, inversely proportional

Bending a wire into a loop ______ the magnetic field inside the loop - why?

concentrates - fields from each segment add constructively in the interior

Strength of field for circular loop of current is_____ to current and ____ to radius of loop - _____coils/loops further strengthen the field

proportional, inversely proportional, multiple

Since electric current exerts a force on magnet, a magnet _______

Also exerts a force on a current carrying wire

Direction of the force exerted on the wire is always ____ to direction of current and _____ to direction of magnetic field

perpendicular, perpendicular

Magnitude of force exerted on wire is product of ____, length of wire, _____, and sine of angle between wire (current direction) and magnetic field

current, magnetic field

For magnitude of force exerted on wire, force is strongest when current is ____ to the magnetic field
If current is _____ to the field (angle between them is zero), force is zero

perpendicular to the field lines
Parellel

Right hand rule for magnitude of force exerted on wire
Thumb goes in current direction, index finger in direction of _____, curl fingers to indicate ____

magnetic field, direction of force

Freely moving electric charged particles (not in wire) experience _____ moving thru magnetic field

a force

For force on electric charge - the force is ___ if particle moves parallel to field lines, and the direction of the force is _____ to magnetic field

parallel, perpendicular

the lorentz force is the force a charged particle experiences when placed in ____
Equation: F = ____

an electric and/or magnetic field
q (E + v x B)

Lorentz: The qE is the ______ - acts in the direction of the _____ for positive charge (____ for negative)

electric force, electric field, opposite for negative

Lorentz: the electric force changes ____ of particle and can ___

speed, can do work on it

Lorentz: the (qv x B) is the _____ - acts ____ both to particle’s velocity and magnetic field

magnetic force, perpendicular

Lorentz: magnetic force does ____ (can’t change speed, only ____), and causes path to _____, often into circular or helical motion

no work, direction, curve

Lorentz: to find direction of magnetic part - point finger in direction of velocity, curl towards ____, and thumb gives direction for positive charge (reverse for negative charge)

magnetic field

A current-carrying loop in a uniform magnetic field experiences a ____ which ___ the loop

torque, rotates

Magnitude of torque is product of number of turns in the loop, _____, area of loop, _____, sine of angle between plane of loop and magnetic field direction

current, magnetic field strength

Torque is max when field is _____ to plane of loop

perpendicular

the hall effect is the generation of a transverse electric voltage across an electrical conductor when it carries ____ in the presence of perpendicular ____

electric current, magnetic field

Hall - when current flows thru conductor and ___ is applied perpendicular to direction of current, moving charged particles experience the Lorentz force, pushing them to 1 side of conductor
This causes accumulation of charge on 1 side, creating a ____across conductor
This electric field _____ further charge separation, resulting in steady state of equilibrium voltage

magnetic field, voltage difference, opposes

Ampere’s law: relates _____ generated around closed loop to ____ enclosed by that loop

magnetic field, total electric current

Ampere’s law: Line integral of ____ around closed loop is proportional to _____ enclosed

magnetic field, current

A solenoid is a long cylindrical coil of wire with many closely spaced turns - when current flows through, it produces a near uniform ____inside the coil

magnetic field

Solenoid - field strength is proportional to number of turns per unit length and ____ passing thru wire
Field outside solenoid is ____

current
Very weak, due to field lines spreading out and canceling

Toroid is coil of wire wound in shape of ____. the magnetic field inside toroid is confined to this shape, forming concentric circular ____ around center of ring

doughnut, magnetic field lines

Toroid - ____ to current and total number of turns, _____ to radial distance from center of ring

proportional, inversely proportional

Biot-savart law: describes the magnetic field generated by ____

steady electric current

Biot-savart: magnetic field decreases with ____ from the current element

square of distance

Biot-savart: field direction is ____ to plane containing current element and point of observation

perpendicular

Biot-savart: total magnetic field at a point due to a wire is the ___ of contributions from all ____elements along the wire

integral, current

if two wires are parallel and carrying current in the same direction, the wires will ____

be attracted to each other

if two wires are parallel and carrying current in opposite direction, the wires will ____

repel each other

Magnetism is caused by _____ and is felt by ____

moving charges

Cyclotron frequency is independent of _____ of particle and _____ of orbit, it depends on ___ ratio of particle in a given magnetic field

velocity, radius, charge to mass

Currents in a bar magnet come from _____

electrons

Maxwell (static) - the lorentz force tells you what the fields do to _____, and the 4 maxwell equations tell you how the fields in turn are determined by ____

charges and currents

Increase in intensity of magnetic field means _____

increase in flux

Increase in area means ____

increase in flux

rotating loop means what for flux?

the flux oscillates

Lenz - the magnetic field induced by the current would ____

oppose the field

If flux is increasing, the induced magnetic field should _____

decrease flux

If flux is decreasing, the induced magnetic field should _____

increase flux

If magnetic field is coming out of plane, induced current should be _____

clockwise

If magnetic field is going into plane, induced current should be

counterclockwise

Faraday - when a loop conductor is placed in magnetic field and the flux changes, _____

emf is generated and a current is induced

Faraday - magnitude of the emf generated is proportional to ____

change of flux with respect to time

Faraday - the emf induced is going to be in direction so to induce a current that will ____

counteract the change in flux

If you have multiple loops of coil, each turn of the coil will ____ strength of emf generated

increase