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9 Je

The document explains the principles of electromagnets, including how current flow creates magnetic fields and how the strength of an electromagnet can be increased by adding more coils, increasing current, or inserting magnetic materials. It also discusses relays, which use electromagnets to control larger currents safely, and the motor effect, where a wire in a magnetic field experiences a force, enabling electric motors to function. To enhance the motor effect, one can increase the current or use stronger magnets.

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6 views17 pages

9 Je

The document explains the principles of electromagnets, including how current flow creates magnetic fields and how the strength of an electromagnet can be increased by adding more coils, increasing current, or inserting magnetic materials. It also discusses relays, which use electromagnets to control larger currents safely, and the motor effect, where a wire in a magnetic field experiences a force, enabling electric motors to function. To enhance the motor effect, one can increase the current or use stronger magnets.

Uploaded by

A Person that needs to download
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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9Je: Electromagnets

Prepared by
Md. Muhaiminur Rahman
Physics & CS Teacher
Lighthouse International School LIS, GB
Current flow and magnetic field

• When current flows inside of a wire it creates


magnetic field around it.
• If the current increases the magnetic strength will also
increase.
• Also the direction of the field changes with the
current’s direction.
2
Current flow and magnetic field

• If a wire shapes as a coil (solenoid) the magnetic


field will be like bar magnet’s magnetic field
shape.

• So, the direction of the magnetic field depends on


which direction the current is flowing.
3
Current flow and magnetic field

4
Strength of the electromagnet
• The strength of the electromagnets depends on number of coils
of wire (how many turns) (N). The more the turn is the more the
strength.
• It also depends on amount of current flow (I). The more the
current the better the strength.
• If we insert a magnetic material inside of the coil it also
increases the strength.

5
Strength of the electromagnet
• The strength of the electromagnets depends on number of coils
of wire (how many turns) (N). The more the turn is the more the
strength.
• It also depends on amount of current flow (I). The more the
current the better the strength.
• If we insert a magnetic material inside of the coil it also
increases the strength.

6
Relays
• A relay is an electrically operated switch that uses a small
electric current to control a larger current in another circuit.
• It works with an electromagnet: when the small current flows
through the relay's coil, it creates a magnetic field that moves a
switch to open or close the larger circuit.
• Relays are commonly used to improve safety, isolate circuits, or
control high-power devices with low-power signals.

7
Relays
• Relays use electromagnets to control circuits.
• By using electromagnet it makes a small current switches on a larger
current.
• As it uses electromagnets we don’t need to touch high-current circuits
directly.
• So it can protect against electric shocks and accidents.
• It is common in devices needing safe circuit control.

8
Relays

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Relays

10
Motor Effect

• When a current flows through a wire, it creates a


magnetic field around the wire.
• If the wire is placed in the magnetic field of a magnet,
the two magnetic fields interact.
• This interaction causes the wire to experience a force,
known as the motor effect.
11
Direction due to motor effect

• The direction of the force depends on two things:


• The direction of the current in the wire.
• The direction of the magnetic field.
• This force occurs only if the wire cuts across the
magnetic field (not parallel to it).
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Diagram

13
Electric Motor
• An electric motor works by using the motor effect.
• It consists of a coil of wire placed in a magnetic field.
• The magnetic field can be created by permanent magnets or
electromagnets.
• When current flows through the coil, the magnetic field from the
coil and the magnets combine, making the coil spin.

14
Electric Motor

15
How to increase the Force due to
motor effect?
• Increase the current flowing through the wire.

• Use a stronger magnet to produce a more


powerful magnetic field.

16
Electric Motor

17

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