# Field Lines - PowerPoint PPT Presentation

PPT – Field Lines PowerPoint presentation | free to download - id: 657c87-M2YwY

The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
Title:

## Field Lines

Description:

### Title: ELECTRICITY and MAGNETISM Author: Jenn Last modified by: Jenn Created Date: 5/18/2009 12:59:11 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

Number of Views:3
Avg rating:3.0/5.0
Slides: 32
Provided by: jenn241
Category:
Tags:
Transcript and Presenter's Notes

Title: Field Lines

1
Field Lines
2
Rules for drawing electric field lines
• At every point the direction of the field is
tangent to the line
• Strength is represented by density
• Lines go from positive and to negative

3
(No Transcript)
4
Rules for Gravitational Field Lines
• The force of gravity is always attractive
• The field lines will always point towards the
center of a spherical mass and arrive
perpendicular to the surface

5
Rules for Magnetic Field Lines
• Field lines leave the N-pole, enter the S-pole
and continue to form a closed loop inside the
magnet
• Magnetic Flux the number of magnetic field
lines passing through a particular unit area.
Proportional to the magnetic field intensity

6
Questions from Provincial Exam Draw appropriate
lines to describe field near the objects shown
• A)
• B)

7
Questions from Provincial
• Three points are indicated as A, B, C on the
diagram. List the letters in order of increasing
field strength (weakest first)

8
Questions from Provincial
• The diagram shows 3 magnetic poles mapped with
iron filings. Identify which two poles are

9
ELECTRICITY and MAGNETISM
10
Rules for Magnetic Interactions
• 1. Like poles repel each other
• 2. Unlike poles attract each other
• 3. The force of attraction varies inversely as
the square of the distance between the poles
• Magnetic Dipole
• Magnets always seem to come with a N-pole paired
with an S-pole

11
ELECTROMAGNETISM
• Electrons produce a magnetic field and a changing
magnetic field will cause electrons to move.
• Discovered by accident in 1819 by Hans Christian
Oersted

12
USES
• Discovery marked the beginning of modern science
and technology
• Radio, television, computers, tape recorders,
VCRs, CD players, lasers, electric motors and
generators, etc

13
Magnetic Fields
• Each point of a current carrying conductor
creates a magnetic field around itself
• The field lines are a set of concentric closed
circles perpendicular to the direction of the
current

14
Right-hand rule 1 finding direction of magnetic
field lines around a conductor
• Grasp a current carrying conductor with a your
right hand, thumb lies in the direction of the
conventional current (positive flow)
• The fingers encircle the conductor in the
direction of the magnetic field lines caused by
the current

15
Magnetic Fields on a Coil
• Field lines are closed loops
• Inside the coil, uniformly spaced to represent
the uniform nature of the field
• Outside, spread out to indicate the weakened
field
• Xs indicate field lines that go into the page
• Dots indicate field lines out of the page

16
Magnetic Fields around a Solenoid
• Solenoid a closely wound helix. The field from
a solenoid is stronger and more uniform.
• The field lines leave one end of the solenoid,
circle around and enter the other end.

17
Right-hand rule 2 finding the N-pole of a coil
of wire
• Place fingers of right hand along the wire of the
coil so that your fingers point in the direction
of the current in the coil
• This will indicate the direction of the field
lines as they pass through the coil, and thus the
face of the coil that acts as the N-pole

18
INTERACTIONS OF MAGNETIC FIELDS
• AMPERE

19
Andre Ampere
• 1820
• Developed mathematical law describing the
relationship between the current in a conductor
and its resulting magnetic field

20
Current in the same direction
• Magnetic fields between the two conductors are in
opposite directions
• The magnetic fields will apply a force drawing
the conductors together

21
Current in opposite directions
• Magnetic fields between the two conductors are in
the same direction
• The magnetic fines of force will repel each other

22
Question from previous provincial
• Two long straight current-carrying wires are
placed so that they are parallel to one another.
The picture shows a cross-section of the 2 wires.
Draw a representation of the field lines and
draw force vectors showing the direction of the
magnetic force on each wire.

23
Questions Section Review
• pg 767 1 a, b, c

24
The AMPERE
• The unit of measure of electric current intensity
• The amount of current in each of 2 long straight
parallel conductors, one meter apart, that will
cause a force of 2 x 10-7N to act on each meter
of wire.

25
The Motor Force
• F kILB
• The force exerted by a magnetic on the magnetic
field of a current carrying conductor
• magnetic field that acts perpendicular to the
conductor (B )
• current (I)
• length of the conductor inside the field (L)
• k is the proportionality constant

26
The Electric Motor
• Activity from resource book

27
Electromagnetic Induction
28
Electromagnetics
• Core of ferromagnetic material placed inside a
solenoid increases the strength of the magnetic
field inside the solenoid
• 3 things affect the strength of the
electromagnet size of current, number of turns
of the coil, permeability of the core

29
Strong Electromagnets
• Must be super-cooled to the point where the coils
become superconductors, and lose their
resistance.
• MRI, High speed trains, Particle accelerators

30