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A Connection Between
Why does a compass
needle point North?
Hans Christian Ørsted
• One day as Ørsted was
experimenting with
electric current, he
noticed that a compass
needle moved next to a
current-carrying wire.
• Ørsted had discovered a
connection between
electricity and
magnetism: electric
current creates magnetic
fields!
Magnetic Field Caused by the
Motion of Charges
a.
b.
When there is no current in the wire, the compasses
align with Earth’s magnetic field.
When there is a current in the wire, the compasses
shift and align around the wire!
Magnetic Field Caused by the
Motion of Charges
a.
b.
When there is no current in the wire, the compasses
align with Earth’s magnetic field.
When there is a current in the wire, the compasses
shift
and align around
A magnetic
fieldtheiswire!
produced by the
motion of electric charges (current).
Making an “Electromagnet”
• If the wire is bent into a loop, the magnetic field lines become
bunched up inside the loop.
• If the wire is bent into another loop, the concentration of
magnetic field lines inside the double loop is twice that of the
single loop.
• The magnetic field intensity increases as the number of loops is
increased.
• A current-carrying coil of wire is called an electromagnet.
Making an “Electromagnet”
Iron filings sprinkled on paper reveal the
magnetic field configurations about
a. a current-carrying wire
Making an “Electromagnet”
Iron filings sprinkled on paper reveal the
magnetic field configurations about
a. a current-carrying wire
b. a current-carrying loop
Making an “Electromagnet”
Iron filings sprinkled on paper reveal the
magnetic field configurations about
a. a current-carrying wire
b. a current-carrying loop
c. a coil of loops
Where does our
electricity come from?
Michael Faraday (1791-1867) discovered that a
changing magnetic field through a coil produces an
electric current!
Investigation Task
Your task is to plan and conduct an investigation
to provide evidence that:
o an electric current can produce a magnetic
field, and
o a changing magnetic field can produce an
electric current.