Electromagnetic Interactions

117

Electromagnetic
Interactions

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118

Magnetism and Electricity

In 1820, Hans Christian Oersted, a Danish Physicist,
demonstrated that magnetism was related to electricity.

By bringing a wire carrying an electric current close to a magnetic
compass he noticed a deflection of the compass needle.

119

Electrical Current and Magnetic Fields

In this diagram, the red lines circling the wire are the magnetic field lines!

An electrical current (moving charge)
placed through a wire produces a magnetic
field around the wire!

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The greater the electrical current, the greater the strength
of the magnetic field produced.

The magnitude of magnetic field produced by a straight
current­carrying wire at a given point is:

• Directly proportional to the current passing in the wire.

• Inversely proportional to the distance of that point from the
wire.

Electrical Current and Magnetic Fields

122

Visualizing Magnetic Fields in the Lab

By sprinkling iron
filings around a
magnet, we see that
they will line up with
the magnetic field of
the magnet.

123

The Right Hand Rule

I

B

Grab a wire with your right hand
with your thumb pointing in the
same direction as the current.

Your fingers point in the direction of the magnetic field!

Right Hand Rule -

*use a pen or pencil to practice*

*helpful reminder -
Right hand rule is used
for wiRes (both have an R)

125

Magnetic Field Around a Coil

The magnetic field around a coil is similar to the field that
we see around a bar magnet.

126

The Left Hand Rule

For a COIL, use the LEFT HAND RULE.
­ When the fingers point in the direction of the current in the loops, your
thumb points in the North direction of the magnetic field

Click for a video on the Left Hand Rule

Left Hand Rule -

*helpful reminder - it works the same as the right hand rule

except Left hand rule is used when a coiL is present (both have a L)

129

Electrical Current and Magnetic Field

How might this be put to
use in our modern society?

We have seen that moving magnetism can can produce
an electrical current in a wire.

130

Michael Faraday­
The Father of Electromagnetism

British physicist and chemist, best known for his discoveries of
electromagnetic induction and of the laws of electrolysis. His biggest
breakthrough in electricity was his invention of the electric motor.

Click here to see a video on Michael
Faraday's Electromagnetism

Multiple Choice

41 Moving electricity causes a magnetic field to form.

• True

• False

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41 Moving electricity causes a magnetic field to form.

True

False

Answer

The electricity runs up or down and

the magnetic field forms around the object.

Multiple Choice

42 The __________ rule is the rule that relates the direction of a magnetic field surrounding a wire carrying current.

• left thumb

• right hand

• right arm

• left hand

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42 The __________ rule is the rule that relates the
direction of a magnetic field surrounding a wire
carrying current.

A
left thumb

B
right hand

C
right arm

D
left hand

Answer

Multiple Choice

43 The father of modern electromagnetic theory is:

• Ben Franklin

• Sir Isaac Newton

• Michael Faraday

• Richard Feinman

Multiple Choice

44 The ________ rule is used to determine the direction of the magnetic field around a current carrying coil.

• right hand

• left hand

• C right thumb

• left thumb

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44 The ________ rule is used to determine the direction
of the magnetic field around a current
carrying coil.

A
right hand

B
left hand

C
right thumb

D
left thumb

Answer