FIELDS - general Answer the following question in the space
provided in your packet: Using your own prior knowledge and life
experience, how do you know gravitational, electric, and magnetic
fields exist? (give specific examples if you can think of any)
Slide 3
Real World Reading Read the article at this site:
http://oceanservice.noaa.gov/education/kits/tides/tide
s06_variations.html
http://oceanservice.noaa.gov/education/kits/tides/tide
s06_variations.html Answer the following question in a 5-6 sentence
paragraph: (answer in the space provided in the packet) What is the
role of gravitation in tidal patterns?
Slide 4
Gravitational Fields
Slide 5
Gravitational Field Drawings - Earth Gravitational field around
the earth the length of the arrows indicate the strength of the
field at that distance from the earth
Slide 6
Gravitational Field Drawings Earth & Moon Interaction 2
different examples Example 1: Moon Earth Example 2: Moon Earth
Slide 7
3. In which diagram do the field lines best represent the
gravitational field around Earth? Answer to gravitational field
question from packet
Slide 8
Answer the following questions about jumping into a pool from a
high diving board, a low diving board, and the side of the pool: 2.
Which will cause you to hit the water with the greatest speed? -
the high dive 3. How does the speed relate to the kinetic energy? -
the greater the speed, the greater the kinetic energy KE = mv 2 4.
What causes you to have that kinetic energy? - the height from
which you jump 5. How is this energy related to the height from
which you jumped? - higher the height, the more total energy you
will have 6. Which will give you the greatest initial gravitational
potential energy? - the high dive; gravitational potential energy
depends upon height relative to the earths surface Pe grav = mgh
Answers to gravitational potential energy questions from packet 7.
A block slides along the frictionless path shown in the figure
below. From greatest to least rank the amount of gravitational
potential energy the block has at the different points labeled on
the track. A.A, B, C, D B.C, D, B, A C.D, C, B, A D.A, B, D, C 8.
As a ball falls freely toward the ground, its total mechanical
energy A. Decreases B. Increases C. Remains the same
Slide 9
Mechanical Energy Gravitational Potential Energy and Kinetic
Energy Mechanical Energy energy acquired/lost by object when work
is done ME = E T = KE + PE = K + U Kinetic Energy (KE or K) energy
of motionK = mv 2 Gravitational Potential Energy (PE or U) stored
energy of position relative to surfaceU = mgh Law of Conservation
of Energy energy cannot be created or destroyed Energy can be
Transferred given from one object to another Transformed changed
from one type of energy into another
Slide 10
9. A ball is dropped from the top of a cliff. Which graph best
represents the relationship between the balls total energy and
elapsed time as the ball falls to the ground? [Neglect friction.]
Answers to gravitational potential energy questions from packet 10.
A child, starting from rest at the top of a playground slide,
reaches a speed of 7.0 meters per second at the bottom of the
slide. What is the vertical height of the slide? (ignore friction)
[hint: remember, the total initial energy = total final energy]
A.0.71 m B.1.4 m C.2.5 m D.3.5 m
Slide 11
Magnets Drawing Magnetic Fields
Slide 12
Magnets Magnetic Fields Magnetic force can be attractive or
repulsive Field lines are vectors Produce CLOSED LOOPS Point from
NORTH to SOUTH outside the magnet Point from SOUTH to NORTH inside
the magnet **Magnets are POLARIZED, which means they have TWO
DISTINCT, OPPOSITE ENDS** Magnetic fields are produced by MAGNETS
& MOVING CHARGES MOVING CHARGES experience magnetic fields like
ELECTRIC FIELDS
Slide 13
Magnets Magnetic Fields
Slide 14
Earths Magnetic Field The earths MAGNETIC SOUTH pole is very
near to the earths GEOGRAPHIC NORTH pole The earths MAGNETIC NORTH
pole is very near to the earths GEOGRAPHIC SOUTH pole
Slide 15
Magnets Natural Magnets: domains inside have ELECTRONS aligned
in their SPINS magnets cause other materials to become POLARIZED
they become temporary magnets; ie: nail or paperclip Permanent
Magnets: domains are PERMANENTLY ALIGNED Non-magnets: domains
inside have ELECTRONS with UNALIGNED SPINS
Slide 16
Not aligned (non-magnetic) Aligned (magnetic)
Slide 17
Answers to magnetic field questions from packet 1. The diagram
below shows the magnetic field lines between two magnetic poles, A
and B. Which statement describes the polarity of magnetic poles A
and B? a. A is a north pole and B is a south pole. b. A is a south
pole and B is a north pole. c. Both A and B are north poles. d.
Both A and B are south poles 2. In which diagram do the field lines
best represent the magnetic field around Earth? 4. When two ring
magnets are placed on a pencil, magnet A remains suspended above
magnet B, as shown below. Which statement describes the
gravitational force and the magnetic force acting on magnet A due
to magnet B? A.The gravitational force is attractive and the
magnetic force is repulsive. B.The gravitational force is repulsive
and the magnetic force is attractive. C.Both the gravitational
force and the magnetic force are attractive. D.Both the
gravitational force and the magnetic force are repulsive
Slide 18
Electric Fields charges change the space around them, this
change is the electric field produced by that charge charges
interact w/each other and exert forces on each other through their
electric fields
Slide 19
Electric Fields Created by Charges & Charged Plates
Slide 20
Properties of electric fields E-fields are produced by charges
and we represent them with arrows (vectors) the lines NEVER cross
but they do bend the closer the lines, the stronger the E-field
(magnitude) E-field lines point in the direction that a positive
charge feels a force (direction) E-field is zero inside a conductor
E-field lines are perpendicular to metallic surfaces Supplemental
electric field information:
http://physics.bu.edu/~duffy/py106/Electricfield.html
http://physics.bu.edu/~duffy/py106/Electricfield.html
Slide 21
Equations Electric Field strength units: N/C or V/m Electric
Force units: N Charge in the field units: C Electrostatic constant
= 8.99*10 9 Nm 2 /C 2 Distance units: m Charge creating the field
units: C Electric Force units: N Distance units: m Charges units: C
Electrostatic constant = 8.99*10 9 Nm 2 /C 2
Slide 22
Answers to electric field questions in packet 15. The center of
a -0.0035 C charge is 0.44 m to the left of the center of an 0.008
C charge. Determine the magnitude and direction of the
electrostatic force on the -0.0035 C charge. F = (kq 1 q 2 )/r 2 =
[(8.99*10 9 )(0.0035)(0.008)]/(0.44 2 ) = 1.3*10 6 N to the right
16. A positive charge is inside an electric field and is
experiencing an electric force to the right. Use words and a
diagram to show the direction in which the field points. Field
points to the right (see slide 19) 17. A negative charge is inside
a leftward pointing electric field. Use words and a diagram to show
the direction in which the charge feels a force. Negative charge
feels a force to the right (see slide 19) 18. An electric field is
measured using a positive charge of 3.0*10 -6 C. This charge
experiences a force of 0.12 N to the right. What are the magnitude
and direction of the electric field strength at the location of the
charge? E = F/q = (0.12N)/(3*10 -6 C) = 4*10 4 N/C to the right 19.
A negative charge of 4.5*10 -6 C produces an electric field. What
is the electric field strength and direction at a distance of 25
cm? 25 cm = 0.25 m E = (kq)/r 2 = [(8.99*10 9 )(4.5*10 -6
C)]/(.25m) 2 = 6.5*10 5 V/m 20. The distance between an electron
and a proton is varied. Which pair of graphs best represents the
relationship between gravitational force, F g, and distance, r, and
the relationship between electrostatic force, F e, and distance, r,
for these particles?
Slide 23
Conductors & Insulators Conductors materials that allow
electrons to move freely from atom to atom Insulators impede the
flow of electrons from atom to atom
Slide 24
Charging by Conduction a neutral object is touched by a charged
object Neutral object either gains or loses electrons to become
charged (protons are NOT transferred) Neutral object becomes
negative gains e- Neutral object becomes positive loses e-
Slide 25
Charging by Induction Charged object is brought near a neutral
object causing polarization Polarization separating opposite
charges within an object
Slide 26
Answers to charging question from packet 21. Two metal spheres
that are initially uncharged are mounted on insulating stands, as
shown below. A negatively charged rubber rod is brought close to,
but does not make contact with, sphere X. Sphere Y is then brought
close to X on the side opposite to the rubber rod. Y is allowed to
touch X and then is removed some distance away. The rubber rod is
then moved far away from X and Y. What are the final charges on the
spheres? Sphere X Sphere Y A. Zero Zero B. Negative Negative C.
Negative Positive D. Positive Negative E. Positive Positive
Slide 27
MAGNETIC FIELD FORCES on moving charges magnetic fields apply a
force to moving charges & current-carrying wires Force on a
charged, moving particle in a magnetic field: F = qvB q = particles
charge (units: coulombs, C) v = particles velocity (units: m/s) B =
magnetic field strength(units: T, Tesla) **How do we determine the
direction of the force?** Right Hand Rule: Relationship between
force, magnetic field, and velocity of a POSITIVE PARTICLE fingers:
DIRECTION OF MAGNETIC FIELD (B) thumb: DIRECTION OF VELOCITY (v)
palm: DIRECTION OF FORCE (F) ***For negative particle, opposite of
right hand rule*** *** a particle must be moving PERPENDICULAR to
the magnetic field *** *** a particle moving PARALLEL to mag. field
will feel NO FORCE (F =0)***
Slide 28
MAGNETIC FIELD FORCES moving charges Determine the direction of
the unknown variable for a proton moving in the field using the
given information: F is down F is left F is out of the page
Slide 29
MAGNETIC FIELD FORCES current-carrying wire Force on a
current-carrying wire in a magnetic field: F = ILB F = FORCE
(units: N) I = CURRENT (units: A) L = WIRE LENGTH (units: m) B =
MAGNETIC FIELD STRENGTH (units: T, teslas) **How do we determine
direction?** APPLY RIGHT HAND RULE THUMB IS CURRENT (I) (instead of
velocity)