applications of electromagnet

8/3/2019 Applications of Electromagnet

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Applications of Electromagnet

1. There are many applications of electromagnets. Label and describe the figure of each

apparatus stated in the table below with its simple work-frame.

1) Electric bells

2) Electromagnetic Relays

1. When the switch is closed, the current

flow will magnetized the soft-iron core

2. The soft iron armature is pulled

toward electromagnet and hit the gong

3. At the same time, the contact will open

and stop the current flows. No

electromagnet.

4. The spring mechanism brings the

armature back to its original position5. The contacts close again and similar

pocess is repeated.

1. When the switch A is closed, a small

current flows in input circuit will

magnetized the soft-iron core

2. The soft iron armature is attracted

toward electromagnet

3. At the same time, the spring contact

closed

4. A large current flows to high voltage

circuit to operate the electrical

apparatus.

batteries

gong

soft-ironcore

springs

contact

soft-iron

armature

soft-ironcore

to high voltage

circuit

switch



3) Telephone earpieces

4) Circuit breakers

5) Lifting Magnet

1. A varying current received from the

caller in telephone line

2. The varying current passes through

solenoid and magnetized the soft-iron

core

3. The electromagnet varies in magnetic

strength according to the verifying

current

4. The alloy diaphragm will attract to

electromagnet by varying force

5. Sound produced as compression and

rarefaction of air particles

Its operate as …………………………

…………………………………………

…………………………………………

1. When the current becomes high (ex:

short circuit) the electromagnet

strength increase suddenly

2. The iron catch is pulled toward

electromagnet

3. The spring pulling apart the contacts

4. The circuit will break and the current

flows stop immediately

Permanentmagnet

solenoid

Alloy

diaphragm

Soft-iron

core

to household

appliancesfrom mainsupply

contacts

automatic switch to breaks

circuit to open when current becomes

too large

spring

Its function to …………………………

…………………………………………

1. Opposite poles on the surface will

produces a stronger magnetic field

2. When the current is switched on, the soft

iron core is magnetized to become a very

powerful magnet

3. Its lifts up iron and steel

4. When the crane has moved to new

location, the current is switched off and

the soft-iron core is demagnetized

3. The objects will fall

move heavy objects or steel

from place to place



3.2: Force Acting on a Current-carrying Conductor in a Magnetic Fields

1. If a current-carrying conductor is placed in a magnetic fields as shown in the experiment,

the conductor will experiences a …………………..

2. Draw the combination (called catapult field ) of two electromagnetic fields below and

show the direction of movement of the conductor.

3. Fleming’s left-hand rule can be use to determine the direction of the force acting or

the motion of the conductor.

+

N S

=

N S

PowerSupply

C-Shapeiron

Magnet

Freelyconductor

Longconductor

force

South pole

North pole



Effect of Two Parallel Current-carrying Coils in a Magnetic Field

4. If two current-carrying conductor is placed in a magnetic fields as shown in the

experiment, the conductor will experience ………………… or ………………….. force

between them.

5. Complete the diagram for current with opposite direction flows in two parallel conductor

below:

6. Complete the diagram for current with same direction flows in two parallel conductor

below:

First Finger ( Field )

Centre Finger ( Current )

Thumb ( Thrust force )

N

repel attract

The two conductor will ……………….. to each other repel



CoilN

S

A

B

currentD

32

4 C

1

commutator

Magnet

Carbon

brush

Turning Effect of a Current-carrying Coil in a Magnetic Field

7. Consider a current-carrying coil ABCD placed between the poles magnet as shown in the

figure below.

8. As the current flows through the coil from A to D, an ….…………….. (1) force acts on the

arm CD whereas a ……………………… (3) force acts on the arms AB according to

Fleming’s Left Hand rule.

Electrical energy Kinetic energy

The two conductor will ……………….. to each other attract

upward

downward



CoilN

SB

A 23

4

1

current

C

D

9. Draw the catapult filed formed and draw arrows to show the movement of arms AB and

CD.

Direct Current Motor

10. Complete the four stages of the motion of DC motor below

00

Through carbon brushes Upwards

Downwards

clockwise

Degree : …………………………

Current flow : Yes / No

…………….…………………..

Arm AB : ……………………….

Arm CD : …………………………

Rotation : ………………………….

Degree : …………………………


…..…………….…………………..

Arm AB : ……………………….

Arm CD : …………………………

Rotation : …………… ……….

900

Circuit broken at carbon brushes right

left

clockwise due to inertia

CoilN

S

current

N S

AB CD



Degree : …………………………


…..…………….…………………..

Arm AB : ……………………….

Arm CD : …………………………

Rotation : ……………

1800

through carbon brushes downward

upward

clockwise

CoilN

S

current

CoilN

S

current

Degree : …………………………


…..…………….…………………..

Arm AB : ……………………….

Arm CD : …………………………

Rotation : …………… ……….

2700

Circuit broken at carbon brushes left

right

clockwise due to inertia



Comparison with Alternating Current Motor

11. Complete the diagram of AC motor below:

Factors that affect the speed of rotation of an electric motor

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

i. Increasing the current flow

ii. Stronger magnet used

13. In conclusion, the speed of rotation of the coil also can increased by:

i. …………………………………

ii. …………………………………

iii. …………….…………………………………

Increasing the current

Using a stronger magnet

Increasing the number of turns on the coils

a.c supply



Moving Coil Ammeter

When current flows in

moving coil, magneticfield of radial magnet

will interacts with

magnetic field produce

by the coil

The force acting causes

the coil to rotate andlead the pointer to the

deflection

The hair spring willrestore the pointer bac

to its original position

The angle of deflection

is directly proportionalto the current flows in

the coil

applications of electromagnet

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