mcat physics chapter 7 magnetism
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in which direction is the magnetic field - in
- electrostatics says that there are electric charges but in magnetism, there is no?
- fundamental magnetic charge
- magnetic fields are created by?
- moving electric ch, currents in wires, and permanent magnets
- magnetic fields exert forces on?
- moving charges, currents in wires, and permanent magnets
- B is a?
- fixed and uniform magnetic field
- si unit of magnetic field is?
- Tesla
- Testla=?
- N(s)/m(C)
- small magnetic fields are measured in?
- gauss
- 1 tesla= __________ Gauss
- 10^4 gauss
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a charge moves in a magnetic field
F from the magnetic field=? - F=qvBsinθ
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F=qvBsinθ
what is B - the strength of the magnetic field
- when a charge moves parallel or antiparallel to a magnetic field the magnetic force is?
- zero
- if a charge moves at θ=0 or 180 to a mag field what happens?
- mag force is zero
-
F = qvB sinθ
what is θ? - θ is the smallest angle betw the vectors qv and B
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F = qvB sinθ
what is q? - q is the charge of the moving particle
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for determining direction of mag force
if q is nonzero and positive ch, then the vector qv _________ as v - points in the same direction
-
mag force
if q is nonzero and neg ch, then the vector qv _________ as v - points in opposite direction
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ch in a magn field
if q or v is zero then the magnetic force? - is zero
- the direct of the magn force will be ________ to the plane defined by qv and B
- perpendicular
-
right handed rule for magn
the ________ of the right hand points in direction of the vector qv (if q is positive) - thumb
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right h rule
the thumb of the right hand points in ? - direction of qv (if q is positive)
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right handed rule
the thumb of rh points in dir of qv, and the fingers point in direct of? - of B
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ch in magn field
right th points in dir of qv, fingers point in dir of B,
and _________ shows you direct of F - which way the palm faces
-
right handed rule for magn
thumb is?
fingers are?
palm is? -
thumb is qv
fingers are B
palm is F- magn force on q -
magn field
symbol x means? -
a field going into the page.
x represents the tail end of an arrow going into the page -
magn field
symbol represents? -
a field coming out of the page
it represents the tip of an arrow coming out of the page -
Suppose a proton, whose charge is +1 .6 x 10-19 C, is moving with a speed of 15 m/s in a direction parallel to a uniform magnetic field of 3.0 T. What is the magnitude and direction
of the magnetic force on the proton? -
since qv and B are parallel
the angle is 0 and the sin of 0 is 0 so
force is zero
F = qvB sin 0 -
Suppose a proton whose charge equals +1 .6 x 10-19 C is
moving with a speed of 15 m/s toward the top of the page
and through a uniform magnetic field of 3.0 T directed into
the page. What is the
direction of the magnetic force on the - the direction of the F is to the left
- Remember the direction of the magnetic force on a negative charge is?
- opposite the direction of the force on a positive charge moving in the same direct as the negat one
- when a ch particle moves perpend to a const uniform magn field the resulting motion is?
- circular motion w a const speed in a plane perpend to mag field
-
charg part mov perp to magn field
the centripetal force is the? -
magnetic force
F=qvBsin90 (sin90 is 1) -
charg part mov perp to magn field
F=qvB= ? - F=qvB=mv^2/r
-
ch part in a magn field
F=qvB=mv^2/r
you can use this to solve for what? -
orbit radius, mang field, etc
r=mv/qB B=mv/qr -
Suppose the proton of the previous example is allowed to
circle (counterclockwise) in the same perpendicular magnet-
ic field of 3.0 T with the same speed of 15 m/s. What is the orbit radius r? (The mass of a proton is
1.67 x 10-27 kg.)
- r=mv/qB
- for a given field direction, if positive charges circle clockwise, then negative charges circle?
- counterclockwise
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electric current
when 2 points at different __________are connected w a conductor, charge flows betw the 2 points - electric potentials
- magnitude of current is?
- the amount of charge i=Δq/Δt
- current is in the directions that?
- positive ch would flow
-
t or f
current is in the direct that posit ch would flow - t
- si unit of current is?
- ampere
- ampere is the si unit of?
- current
- 1A= ?
- 1 coulomb/second
- 1 c/s=
- 1 A
- since electrons are negativ cha they go from _________ potent to ___________ potent
- low to high potential
- by convent direc of current is direct posit ch would flow which is from ________ potent to __________ potent
- high to low
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force on current carrying wire due to magn field
F=? - F=iLBsinθ
-
force on current carrying wire due to magn field
iLBsinθ is equal to what? - the F due to the magnetic field
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right hand rule for force on a current carrying wire in a magn field
thumb of rh points in? - DIRECTION of current i
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right hand rule for force on a current carrying wire in a magn field
fingers of rh point in? - direction of B
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right hand rule for force on a current carrying wire in a magn field
right hand rule
thumb?
fingers?
palm? -
thumb- direct of i
fingers- direct of B
palm- F - the magn force on current carrying wire -
Suppose a wire of length 2.0 m is conducting a current of 5.0 A toward the top of the page and through a 30 Gauss uni-
form magnetic field directed into the page. What is the direction of the magnet-
ic force on the wire? - force on wire is to the left
-
Suppose a wire of length 2.0 m is conducting a current of 5.0
A toward the top of the page and through a 30 Gauss uni-
form magnetic field directed into the page (see figure
7.3(a)). What is the magnitude and direction of the magnet-
-
to convert gauss into tesla
1 T= 10^4 Gauss - 10^4 Gauss= __________ Tesla
- 10^4 Gauss= 1 Tesla
- if a wire has no current moves thr a magnetic field what happens?
- nothing. wires w no curr are electric neutral. no magn force is generated
-
Suppose a wire of length 2.0 m is conducting a current of 5.0
A toward the top of the page and through a 30 Gauss uni-
form magnetic field directed into the page. What is the magnitude and direction of the magnet-
ic force on the wire?
-
F = iLB sinθ = iLB
=5.0(2.0)(3.0)X 10-3) - any moving charge creates a?
- magnetic field
- differ ways to gener a magn field?
-
1. flow of ch in perman magn
2. electric curr
3. indiv moving ch - it is the _____________ that gives rise to the magnetic field
- movement of ch
-
magnetic field lines
magnetic field is ____ to the magn field line at any point - tangent
- _____________ can be used to visualize the magnetic field
- magnetic field lines
- magn materials are classified as?
-
1. diamagnetic
2. paramagnetic
3. ferromagnetic - diamagnetic material are?
- indiv atoms have no net magn field. will be repelled from pole of a strong bar magn. called weakly antimagnetic
- which magnetic material is weakly antimagnetic?
- diamagnetic
- in a ______________ the individ atoms have no net magn field
- diamagnetic material
- paramag material is _____________ magnetic
- weakly
- in paramag and ferromagnetic mat the indiv atoms do have a ?
- net magn field but they are randomly oriented so net magn field.
- ferromagnetic materials below the critical temperature called _______ can dev a higly aligned magn field
- Curie temperature
- above the Curie temp the ferromagnetic material is ?
- paramagnetic
- _________ are called strongly magnetic
- ferromagn
-
t or f
iron, nickel, and cobalt are ferromagnetic - t
- when the north pole of a compass magnet points along local field lines of earths mag field it is pointing?
- towards a magnetic south pole
- on earth, what we call the northern direction is really?
- the direction of a magn south pole
- what is the name of the critical temp below which a paramagn mater bec ferromagn?
- curie temperat
- north pole is place where magnetic field lines?
- emerge
- south pole is where magn field lines?
- enter
- the _________ pole is where magnetic field lines emerge
- north
- the _______________ pole is where magnetic field lines enter
- south
-
t or f
a current carrying wire will prod a magnetic field in its vicinity - t
- the mag f of a curr carrying wire is the _______ of the magn f due to indiv moving ch of the curr
- vector sum
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an infinitely long str wire w curr
B= - B= µoi/2Ϭr
- µo is
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the permeability of free space
= 4Ï€ X 10-â· Tesla∙meter/ampere - what are the units of µo?
- Tesla∙meter/ampere
- µo=
-
=4π X 10-ⷠTesla∙meter/ampere
=1.26 X 10-6 T∙m/A - for a long str wire the magn field strenght __________ with distance
- drops off
- magnetic field lines __________ currents
- encircle
-
current carrying wire
right hand rule
right thumb is?
fingers? -
right thumb is in direct of current
fingers curl in direction of generated mag field B -
A straight wire carries a current of 5 A toward the top of the
page. What is the direc-
tion of the magnetic field at point P, which is 10 cm to the
left of the wire? - B is coming out of the page.
- magn field at the center of a circular loop of curr carrying wire of radius r is?
- B=µoi/2r
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B=µoi/2r
only gives the magnetic field at? - one point in space, the point at the center of the loop
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Suppose a wire is formed into a loop that carries current
clockwise (that is, electrons flow counterclockwise) Find the direction of the magnetic field pro-
duced by this loop:
a. within the loop.
b. outside of the loop. -
a. into the page
b. outside the loop. B will point out of the page. -
A negative charge placed in an external magnetic field circulates
counterclockwise in the plane of the paper as shown below. In which
direction is the magnetic field pointing - out of the page
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If, as in the accompanying figure, an electron is travelling straight
out of the page crossing a magnetic field that is directed from left to
right, in which direction will t - downward, dont forget its an electron so its opposite.
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A long straight wire carrying current I is placed between the poles of
a horseshoe magnet as shown in the figure below. Does the force on
the wire depend on the width of the - yes, F=iLB so the wider the pole face, the more wire that is in the magnetic field and the force can be stronger
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A positively charged particle enters a region with a uniform electric
field, as shown, and is initially moving perpendicular to the field. In
what direction must a uniform magnetic field be oriented so that the
net force on the particle is -
heading out of the page, it will creat a magnetic force F=qvBsin angle downwards, electric field is creating a force pushing the charge up