21.1 Magnets & Magnetic Fields

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Transcript 21.1 Magnets & Magnetic Fields

Assessment Questions 1-8
Generating electric current
 Electric current creates a magnetic field
 LT #2: Demonstrate and explain that an electric
current flowing in a wire will create a magnetic field
around that wire (electromagnetic effect) [Motors]
 A magnetic field can be used to produce an electric
current = electromagnetic Induction = generator effect
 LT #3: Demonstrate and explain that moving a
magnet near a wire will cause an electric current to
flow in the wire (the generator effect) [Generators]
1. How is voltage induced in a
conductor?
 Conductors are materials through which charge
can flow easily (metal wires)
 Voltage is induced in a conductor by a changing
magnetic field.
 So if you move a magnet near a conductor electric
current is generated
2. Name two types of generators.
 AC = alternating current; charges flow in one
direction then reverse direction & converts
mechanical energy into electrical energy
 LT #1: Demonstrate and explain that an electric
current flowing in a wire will create a magnetic field
around that wire (electromagnetic effect)
 DC = direct current; the current that leaves the
generator flows only in one direction
 Most power plants use AC because sending power over
long distances & DC causes too much heat in wires
3. How does a transformer work?
1) A transformer increases or decreases voltage and
current of 2 linked AC circuits
2) It changes voltage and current by generating a
changing magnetic field in one coil.
3) This field then induces a current in a nearby coil with
a different # of turns.
4) We need transformers to step up power to send it
over long distances & step down power to make it
safe to use in homes
4. Name the 6 sources of electrical
energy in the United States.
 Coal
 Nuclear power
 Water = hydroelectric
 Wind
 Natural gas
 Petroleum
5. How can water be used to create
electrical energy?
 Water can turn a turbine (PE  KE mechanical)
 The turbine turns an axle of a generator & produces
electricity (mechanical  electrical)
 LT #1: Describe a situation where energy is
transformed from one form to another.
6. What is the connection between
Faraday’s law & the generation of
electrical energy?
 Faraday’s law = a voltage is induced in a conductor by a
changing magnetic field
 The relative motion of a magnet & a coil of wire will
cause charges to flow in the wire generating electric
current and electrical energy
7. How are AC & DC alike? How
are they different?
 Both produce electric current by rotation of wire coil
in a magnetic field
 In a DC generator current only flows in one direction
8. Why can’t we use electrical
energy directly from a high voltage
line?
 We’d fry!
 High voltages are dangerous & household devices are
designed to use much lower voltages