ELECTROMAGNETS

Objectives:2.4 Demonstrate the effect of a core on the

behavior of an electromagnet2.5 Explain the properties of magnetized matter

using the simplified atomic model.2.6 Factors that affect the magnetic field of an

electromagnet2.7 Determine the mathematical relationship

that affects the magnetic force of an electromagnet.

Factors that affect the Magnetic field of an Electromagnet

1. The core material The denser the material the stronger

the field

2. The current intensity Higher the current stronger the

magnetic field

3. Number of loops (number of turns)

More turns gives a stronger field.

Important

Factors that Affect Magnetic Field

Core material

Number of loops (turns)

Current Intensity

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.

Do not want a

permanent magnet for the core

Core Material

Ferromagnetic cores strengthen the magnetic field Iron, Steel, nickel & cobalt Iron is a VERY GOOD core

Wood, plastic and Aluminum are not very good products for a core

Number of Loops

As the number of loops increases, the strength increases

Few loops Many loops

Current Intensity

As the current intensity increases, the strength increases

I = 5 amps I = 10 amps

Which has a stronger magnetic field?

A B

Iron Wood

1 - Number of loops is the same2 – Intensity is the same3 – But the core is different

I = 5 amps I = 5 amps

Result:(A) Iron is better because it is a ferromagnetic core

Which has a Stronger Magnetic Field

A B Iron Iron

# of loops are different Intensity is the same Core is the same

I = 2 amps I = 2 amps

3 loops 5 loops

Result:B is stronger: more magnetic loops = a stronger magnetic field

Which has a Stronger Magnetic Field

A B Iron Iron

# of loops is the same Intensity is different Core is the same

I = 2 amps I = 10 amps

5 loops 5 loops

Result:B is stronger because current intensity is greater

Which has a Stronger Magnetic Field

A B Nickel Nickel

Whenever the loops & the current intensity are different but the cores are the same, use the following equation

I = 5 amps I = 2 amps

3 loops 5 loops

Strength of field = current intensity x (# of turns)A 15 = 5 amps x 3 turnsB 10 = 2 amps x 5 turns

A therefore has a stronger magnetic field

Mathematical Relationship

To find the strength of the electromagnet scientists use the following equation: F = IN F is force or strength of the

electromagnet I is the current intensity traveling

through the wire N is the number of loops around the

core

Remember

Which Electromagnet has the Strongest Magnetic Field

Current = 10ATurns = 6

Current = 7ATurns = 10

60 = 10A x 6 turns 70 = 7A x 10 turns

Strongest

Factors affecting magnetic field: Core material,

Iron is always the best core material

Number of turns The more loops the stronger the field

Current Intensity High current results in stronger intensity

Origins of Magnetism of Matter

Scientists believe that magnetism comes from spinning electrons around the nucleus of the atom.

When atoms clump together they form a domain.

Enrichment

Similar electron spins produce a strong domain, where as opposite electron spins cancel one another out and produce a weak domain.

If enough domains align in the same direction, this will create a magnetic field.

Origins of Magnetism of Matter

Enrichment

How to Magnetize an Object

Bring the ferromagnetic substance in contact with another magnet.

Bang the ferromagnetic substance (example: striking a nail repeatedly).

Heat up the substance and cause the domains to align.

Run electric current through the ferromagnetic substance.

Please note that all of these methods can also de-magnetize a magnet.

Enrichment

Activities

Student Study Guide Module II – 13 # 1 - 5 Module II - 14 Module II –15 Sec. 2.8

Worksheet # 7

References

Student Study Guide Physical Science 416 – MEQ

Science Quest, Grenier, Daigle & Rheaune, 1998 Editions Cheneliere

Animation Factory Google Images

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