1. A solenoid is a coil of wire wrapped around a cylindrical core that produces a magnetic field when electric current passes through it. 2. The magnetic field pattern of a solenoid resembles that of a bar magnet, with north and south poles at opposite ends. 3. Different core materials, such as iron, steel, nickel, or cobalt, placed inside the solenoid influence the strength of the magnetic field produced.

1. SOLENOIDS
Objectives:
2.3 Map the magnetic field around a
current bearing:
a) straight line conductor
b) solenoid

2. Solenoid
 Wire wrapped around a
core (tube)
 Have a current flowing
through them
 Have a magnetic field
 Their magnetic fields
look like the magnetic
field around a bar
magnet.
Electromagnet

3. Cores
 A Core is the object that is inserted
into the solenoid, creating an
electromagnet.
 Different materials influence the
strength of the electromagnet.
 Different metals can be used for the
core: iron, steel, nickel or cobalt.
 Iron is most commonly used because
when you turn off the electricity it
demagnetizes.
 Metals like steel remain magnetized
thus creating a permanent magnet.

4. Solenoid
 2 Methods
 Right Hand rule
 Left Hand rule
 Either Method works

5. Solenoid Rules – Right Hand Rule
 Step #1: Place palm of right hand on
positive end.
Finding
North & South
Poles
- +

6. Solenoid Rules – Right Hand Rule
 Step #2: At the positive end, look
to see if the wire is in front or
behind the middle tube.
Wire is in
Front of the core
At positive end.
+-

7.  Step # 3: If the wire is in front of
the tube at the positive end, place
your hand on top of the core.
Solenoid Rules – Right Hand Rule
- +

8.  If the wire is behind the tube at the
positive end, place your hand under
the tube.
Solenoid Rules – Right Hand Rule
- +
Palm Up
Hand under tube

9.  Step # 4. Double check both palm
and fingers.
 Step #5. Thumb points towards
North. The other end is South.
Solenoid Rules – Right Hand Rule
- +

10. Solenoid Examples - # 1
1. Go to the
positive
2. Wire runs behind
core
3. Hand goes under
core & fingers
curl up
4. Thumb points N.
Other end is S.
5. Lines of Magnetic
force run N
(Nerd) to S
(Sexy).
+-

11. Solenoid Example # 2
1. Find Positive
2. Wire runs in
front of core
3. Place hand on
positive
4. Thumb points
to North
5. Other end is S
6. Magnetic field
runs N (Nerd)
to S (Sexy).
-+

12. Activities
 Work Sheet Mod II, # 3
 Observatory, p. 174, Q. 25

13. Effects of Placing a Compass Near a
Solenoid
1. Label North and South.
2. Draw in arrow on compass.
Example #1
- +
Compass
Remember
That the
Needle is
North
Needle points
to
South

14. More Examples
1. Label North and
South.
2. Draw in arrow on
compass.
Example #2
-+
Compass

15. When Two Solenoids Meet
 Answer: Solenoids would attract.
Would they attract or repel?
+ -
- +
Likes
Repel &
Opposites
Attract

16. Solenoid without a + or -
In a battery
the longer line is
ALWAYS
positive
First
Find the
positive
+ -

17.  Right Hand Rule: Use only the right
hand to label N and S.
 Before solving a problem, always label
N and S first.
 Red Compass needle is North and
is attracted to South.
 When the + and the – are not given
on a diagram, remember that the
longer line on the battery is always
positive.

18.  Wires with electricity flowing through them
 Like solenoid have N and S poles and
magnetic field.
Straight Line Conductor

19.  Step # 1: Using your right hand,
point your thumb towards the
negative post
Straight Line Conductor
Right Hand Rule
- +
Hand on top
in this
situation

20. Straight Line Conductor
Right Hand Rule
-+
Or hand behind
the conductor
As long as the
thumb points to
negative

21.  Step # 2: With your hand open,
your finger nails are South and your
knuckles are North.
Straight Line Conductor
Right Hand Rule
+-

22. Straight Line Conductor
Right Hand Rule
If your hand is
behind the wire
and you cannot
see your finger
nails, close your
hand.
-+
-+
Knuckles are
up (N)
Nails are down
(S)

23. Placing N & S –
Straight Line Conductor
+
+
+
+
-
-
-
-

24. Effects of a Compass on a
Straight Line Conductor
- +
Compass arrow
Always points
South
Compass

25. Straight Line Conductor
Examples
-
-
-
- +
+
+
+
A B
C D

26.  Right Hand Rule for Straight Line
Conductors – Thumb points to
negative
 North and South are never on the
ends of the line
 Remember that compass needle is
North and is attracted to South
(Southern Bell)
 Finger tips are South and knuckles
are North

27. Activity
 Worksheet Module 2, # 5

29. Important Symbols & Facts
 Magnetic field: represented by B.
 Current: represented by I.
 Magnetic Poles:
 North pole (N)
 South Pole: (S)
 Magnetic Field: Circular around a
straight line.

30. Solenoid Left Hand Rule
 Determine direction by the Left Hand rule
– fingers wrap in the direction of the
electron flow and thumb points in the
direction of the magnetic field (N).
e-

31. Straight Line Conductor
 Current (I):
 flow of electrically charged
particles through a
conductor
 Conventional Current
 Traditionally scientists believed that
current was positive.
I
+

32. Straight Line Conductor
Left Hand Rule
 According to the flow of
electrons, your thumb (left
hand) follows the direction
of the electrons.
 Fingers wrap around the
wire, giving the shape and
direction of the magnetic
field.
e-
B
e-
+-
JJ Thomson
Electricity produced by
electrons
Electron flow