electromagnet 8.2 student copy

8/17/2019 Electromagnet 8.2 Student Copy

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FORM 5© COPYRIGHT BY SUPER EDUCATION GROUP (J

CHAPTER 8: Electr!"#$et8%& Fle!'$# et H"$* R+le


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CHAPTER 8: Electr!"#$et

1. If a current carrying coil is placed in a magnetic field (As shown in diagram above), a pair of forces will

be produced on the coil. This is due to the interaction of the magnetic field of the permanent magnet and

the magnetic filed of the current carrying coil.

2. The diagram below shows the catapult field produced.

PREPARED BY JJ MREON P"#e ,© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)


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The direction of the force can be determined by Fleming's left hand rule.

3. Since the current in both sides of the coil flow in opposite direction, the forces produced are also in

opposite direction. The 2 forces in opposite direction constitute a couple which produces a turning

effect to make the coil rotate.

4. !amples of electric e"uipment whose operation is based on this turning effect are

a. the direct current motor

b. the mo#ing coil meter.

PREPARED BY JJ MREON P"#e &© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)


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PREPARED BY JJ MREON P"#e -© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)


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P.er S+//l0

C1S2"/e 'r$

M"#$et

Freel0 c$*+ctr

$# c$*+ctr


$.2% Force &cting on a urrent(carrying onductor in a )agnetic Fields

1. If a currentcarrying conductor is placed in a magnetic fields as shown in the e!periment, the conductor

will e!periences a """""""..

2. #raw the combination (called catapult field ) of two electromagnetic fields below and show the

direction of movement of the conductor.

$. Fleming*s left(hand rule can be use to determine the direction of the force acting or the motion of the

conductor.

PREPARED BY JJ MREON P"#e 3© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

SNSN

=+

First Finger ( Field )

Thumb ( Thrust force

N

Centre Finger ( Current


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Efect o Two Parallel Current-carrying Coils in a Magnetic Fiel

,% I t. c+rre$t1c"rr0'$# c$*+ctr '4 /l"ce* '$ " !"#$et'c el*4 "4 42.$ '$ t2e

e6/er'!e$t7 t2e c$*+ctr .'ll e6/er'e$ce r %% rce

9et.ee$ t2e!%

&% C!/lete t2e *'"#r"! r c+rre$t .'t2 o!!osite *'rect'$ .4 '$ t. /"r"llel

c$*+ctr 9el.:

-% C!/lete t2e *'"#r"! r c+rre$t .'t2 same *'rect'$ .4 '$ t. /"r"llel

c$*+ctr 9el.:


T2e t. c$*+ctr .'ll %% t e"c2 t2er

T2e t. c$*+ctr .'ll %% t e"c2 t2er


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The strength of the force can be increased by%

a. Increase the current

b. %sing a stronger magnet

c. using a longer wire

d. Arranging the wire perpendicular to the direction of the magnetic field .

Turning ffect of a urrent(carrying oil in a )agnetic Field

1. &onsider a currentcarrying coil A' placed between the poles magnet as shown in the figure below.

2. As the current flows through the coil from A to #, an ".+++++.. (1) force acts on the arm

whereas a +++++++++ ($) force acts on the arms A' according to Fleming*s eft -and rule.

$. #raw the catapult filed formed and draw arrows to show the movement of arms A' and .

PREPARED BY JJ MREON P"#e ;© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

upward

downward

N C'l

S,

"

Carbon

brush

C3&

-#

M"#$et

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commutator

%inetic energyElectrical energy

CDAB

F

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PREPARED BY JJ MREON P"#e <© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

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N

"

#

&

-

3

,+rre$t

C$

C'l

N

S+rre$t

C'l

N

Sc+rre$t

A

B

D

C


irect urrent )otor

&arbon 'rush To complete the circuit when it is in contact with commutator.

&ommutator To reverse the direction of the current in the coil for every half rotation of the coil so that the rotation remain

in one direction only.


#egree """"""""""

&urrent flow /es *o

"""""."""""""..

Arm A' """"""""".

Arm """"""""""

+otation """""""""".

#egree """"""""""

&urrent flow es 0o

".."""""."""""""..

Arm A' """"""""".

Arm """"""""""

+otation """"" """.

&

#

'

#egree """"""""""

&urrent flow es *o

".."""""."""""""..

Arm A' """"""""".

Arm """"""""""

+otation """""


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C'l

N

S+rre$t


omparison with &lternating urrent )otor

PREPARED BY JJ MREON P"#e =© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

#egree """"""""""

&urrent flow es *o

".."""""."""""""..

Arm A' """"""""".

Arm """"""""""

+otation """"" """.

'

&

#

"%c

4+//l0


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Factors that affect the speed of rotation of an electric motor

1. The magnitude of force acting on a conductor in a magnetic increases by

i. Increasing the current flow

ii. -tronger magnet used

2. The speed of rotation of the coil also can increased by

i. """""""""""""

ii. """""""""""""

iii. """""."""""""""""""

iv. """"""""""""""""""

v. """"""""""""""""""".

)o#ing oil &mmeter

PREPARED BY JJ MREON P"#e ,>© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

$

?2e$ c+rre$t .4 '$

!@'$# c'l7 !"#$et'cel* r"*'"l !"#$et

.'ll '$ter"ct4 .'t2

!"#$et'c el* /r*+ce

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T2e 2"'r 4/r'$# .'ll

re4tre t2e /'$ter9"c t 't4 r'#'$"l

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T2e rce "ct'$#

c"+4e4 t2e c'l t

rt"te "$* le"* t2e

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T2e "$#le *eect'$

'4 *'rectl0 /r/rt'$"l

t t2e c+rre$t .4 '$

t2e c'l


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ight 1ndicator ,% & light indicator which has lower inertia is used to increase

the sensiti#ity of the meter.

inear Scale . ue to the radial magnetic field and the cylindrical soft(

iron core, a linear scale is produced.

2. & linear scale is more accurate and easier to be read.

)irror

. & mirror is used to pre#ent paralla! error.

2. hen the obser#er's eye is e!actly abo#e the indicator, the

indicator will co#er its own image on the mirror.

ur#ed ermanent )agnet

. & cur#ed permanent magnet is used to produce a radial

field.2. & radial field is a magnetic field where the field lines are

either pointing away or toward the center of the field.

3. & radial can be focused by a cylindrical soft(iron core.

5ectangular oils

. hen a current flows through the coils, a force will be

generated due to the interaction between the magnetic field

of the permanent magnet and the coil.

2. The force will turn the coils, which in turn mo#e the

indicator.

ylindrical Soft(1ron ore . & cylindrical soft iron core is placed inside the radial field

produced by the cur#ed magnet.

2. & soft(iron core can focus the magnetic field of the

permanent magnet.

-air Spring

. The deflection of the coil and the indicator stops when the

force is balanced by the opposing force from the hair

spring.

2. The angle of deflection is directly proportional to the

magnitude of the current in the coil.

PREPARED BY JJ MREON P"#e ,,© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

electromagnet 8.2 student copy

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