electromagnet 8.1

8/18/2019 Electromagnet 8.1

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FORM 5© COPYRIGHT BY SUPER EDUCATION GROUP (J

CHAPTER 8: Electr!"#$et%&5 Electr'c"l E$er# P*erE+c'e$c


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N S

Direction of magnetic elds

CHAPTER 8: Electr!"#$et

Newton Memory

1. Electromagnet is a temporary magnet consist of a long coil of

insulated copper wire carrying electric current wound on a soft iron

core./temporary magnet produces by the flow of current.

2. The magnetic effect of current is called electromagnetism which

means that electricity produces magnetism.

3.

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

Permanent Magnet Temporary Magnet

"& it is made of steel

.& the strength of the

magnetic field is

normally constant and is

not adjustable

"& it is made of iron cobalt and

nic!el

.& The strength of the magnetic

field is adjustable or random.

c& both ha"e similar magnetic effect./& both magnet ha"e two pole #North Pole and $outh Pole%


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&.1' Magnetic Effect of a current(carrying conductor

Electromagnets

1. Conductor is a material that can flow ……………………..

2. Electromagnetism is the study of the relationship between ……………….and ………………..

3. ………………………. are produced by electrically charged objects.

4. A bar magnet produces the ………………………around it. raw the pattern of the magnetic fields

produced around a bar magnet below

PREPARED BY JJ MR,EON P"#e 0© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

current

magnetismelectricity

Electric felds

magnetic felds


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N S

S1t 'r$ cre

I$23l"te/ *'re

4'$2

DC 2344l

*'tc

S1t 'r$ cre

I$23l"te/ *'re

4'$2

DC 2344l

*'tc


!. "how the deflection of the pointer of the compasses.

#. $agnetic fields also can be produce by an electric current in a wire.

%. Electromagnet is a ………………… magnet. &t is made by winding a coil of insulated wire round a soft

iron core.

'. (sing the diagram) complete the steps to switch on the magnetism effect.


temporary

Electrom

agnetic

fled

Sot iron

core is

magnetis

Current

ows

S*'tc '2

cl2e/

Attracts

pins


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Direction of magnetic elds


). Magnetic *ield due to a +urrent in $traight ,ire

Method ' using +ompass and -ron filling used to map out the pattern of the magnetic field

1. (sing ight(hand /rip ule) draw the direction of current flows and pattern of magnetic fields formed

2. ight(hand /rip ule states that the thumb of the right hand points to the direction of current flow

and the other four curled fingers points to direction of its ………………….

3. raw the same patterns from the top *iews as follows together with the direction shown by the

compasses.

$eans that a wire carrying current ………….. the plane of paper

$eans that a wire carrying current …………... of the plane of paper


magnetic

into

out


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E0ercise &.1

1. +wo small plotting compasses , and - are placed near a long straight wire carrying a current as shown.

"how the directions shown by the pointers of the compasses

4. &n the diagram below) the compasses are put under the conductor. Can you draw the direction shown by

compasses and what happen if the compasses are put on the conductor

. Magnetic *ield due to a +urrent in a +ircular +oil

!. raw the direction of current flows and pattern of magnetic fields formed.


P

Te c!4"22 '2

43t UNDER te

Te c!4"22 '2

43t UNDER te


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#. +he direction of magnetic field also can be determined using the ightand /rip ule.

/ 0otes The field strength is the strongest at the center area because combination from two sources

+he magnetic field strength can be increased by increasing the current flow in the wire.

i adding more battery or cell in the series ciruit

iireducing the resistance by busing the rheostat

iii using a shorter wire

i*using a thicer wire

+he strength of magnetic field of the coil wire increase when

i when the current in the coil increased

iithe number of turn of coil increase

iii a coil with smaller radius is used

+. Magnetic *ield due to a +urrent in a $olenoid

1. $olenoid is combination of coils of wire wounded around on some surface or wounded around an iron

core.



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2. +o chec the poles formed) see from beside of the

solenoid. &f the current flow is cloc!wise) the polarity on

that side is …………………… but) if the current flow is

anti(cloc!wise) the polarity on that side is

……………………

the strength of magnetic field of solenoid increase when

#i% the magnitude of current increase

#ii% the number of turns is increased

#iii% a soft iron core is placed in the solenoid

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

North

South


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#i"%the turns of the wire are pushed closer together so that the solenoid become shorter

produce higher field strength.

4.*actors that affects the strength of an electromagnet

15.

+he

higher the number of paper clips attracted to the solenoid shows the …………..….the strength of that

electromagnet.

As a conclusion) fill the table below

Factors Conditions Number of paper clips

attracted

Affects on the strength of

electromagnetic fields

0umber of turns

Electric current

(se of normal iron6core

-nil-(se of soft6iron core


Manipulated Responding Fixed

0umber of turns Number of paper clips attracted Current) types of core

Current 0umber of paper clips attracted 0umber of turns) types of core

+ypes of core 0umber of paper clips attracted Number of turns, Current


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)pplications of Electromagnet1. +here are many applications of electromagnets. 7abel and describe the figure of each apparatus stated in

the

table

below with its simple wor6frame.

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

1) Electric bells 2*'tc

-& When the switch is closed, the

current fow will magnetized the sot-

iron core

0& The sot iron armature is pulled

toward electromagnet and hit the

gong

6& At the same time, the contact will

open and stop the current fows. No

electromagnet.

7& The spring mechanism brings the

armature back to its original position

5& The contacts close again and similar

process is repeated.

."tter'e2

21t;'r$

"r!"t3re

c$t"ct

24r'$#2

21t;'r$

cre

#$#


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2) Electromagnetic elays

!) Telephone earpieces//spea"ers

PREPARED BY JJ MR,EON P"#e -<© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

-& When the switch A is closed, a small

current fows in input circuit will

magnetized the sot-iron core

0& The sot iron armature is attracted

toward electromagnet

6& At the same time, the spring contactclosed

7& A large current fows to high oltage

circuit to operate the electrical

apparatus.

21t;'r$

cret '#

=lt"#e c'rc3't

-& A arying current receied rom the

caller in telephone line

0& The arying current passes through

solenoid and magnetized the sot-

iron core

6& The electromagnet aries in

magnetic strength according to the

eriying current

7& The alloy diaphragm will attract to

electromagnet by arying orce

5& !ound produced as compression and

rareaction o air particles


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5% +ircuit brea!ers

6% 7ifting Magnet

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

S1t;'r$

cre

All

/'"4r"#!

Per!"$e$t

!"#$et

2le$'/

automatic switch to

breaks circuit to open when

current becomes too large

It2 4er"te "2 >>>>>>>>>>

>>>>>>>>>>>>>>>>>>>

>>>>>>>>>>>>>

-& When the current becomes high

"e#$ short circuit% the electromagnet

strength increase suddenly

0& The iron catch is pulled toward

electromagnet

6& The spring pulling apart the

contacts

7& The circuit will break and the

current fows sto immediatel

24r'$# c$t"ct2

1r! !"'$

2344l

t

32el/

It2 13$ct'$ t >>>>>>>>>>>>>>>>>>>>>>>>>>

-& &pposite poles on the surace will

produces a stronger magnetic 'eld

0& When the current is switched on, the

sot iron core is magnetized to become

a ery powerul magnet

6& (ts lits up iron and steel

7& When the crane has moed to new

location, the current is switched o) and

the sot-iron core is demagnetized

6& The ob*ects will all

moe heay ob*ects or

steel rom place to place


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E0ercise &.1.2

1. A magnetic field is produced by the current in a long straight wire. +he strength of the magnetic field

increases if.

A +he magnitude of the current increases

8 +he distance from the wire increases

C +he length of the wire increases

2. 9hich of the following is true about the magnetic field produced by a current in a flat circular coil.

A &t is uniform inside the coil

8 &t is the weaest at the centre

C &t is the strongest at the centre

+here is no magnetic field outside the coil

3. 9hat is the effect of placing a piece of soft iron core inside a solenoid carrying current

A +he resistance of the solenoid decreases

8 +he current in the solenoid increases

C +he magnetic field becomes stronger

4. An electromagnet is used in these apparatus e0cept

PREPARED BY JJ MR,EON P"#e -0© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

Nrt Ple

S3t Ple


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A a compass

8 an a.c dynamo

C a mo*ing coil ammeter

a telephone earpiece

!. 9hich electromagnet is the strongest

A 8 C

PREPARED BY JJ MR,EON P"#e -6© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)

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electromagnet 8.1

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