Transcript Electricity & Magnetism

Electricity & Magnetism
Static, Currents, Circuits
Magnetic Fields & Electro Magnets
Atoms…
 Have
neutrons, protons, and
electrons.
 Protons are positively charged
 Electrons are negatively charged
Electrons…
 Are
located on the outer edges of
atoms…they can be moved.
 A concentration of electrons in an
atom creates a net negative
charge.
 If electrons are stripped away, the
atom becomes positively charged.
The world is filled with electrical
charges:
+
Electricity is the energy associated
with charged particles
+ +
+
+ +
+
+
+
+
-
What is this electrical potential
called?
 Static
-
Electricity
-
- -
+
++
++
Static Electricity
 The
build up of an electric charge
on the surface of an object.
 The charge builds up but does not
flow.
 Static electricity is potential
energy. It does not move. It is
stored.
Methods of Transfer…
 Occurs
when there is a loss of
static electricity due to three
possible things:
Friction
- rubbing
Conduction – direct contact
Induction – through an electrical
field (not direct contact)
Visualizing Lightning
Turn to page 199.
 Answer the following questions

When the warm humid air rises to meet the
cold air, what causes the air masses to churn
together
 What electrical property causes the negative
charges in the cloud to be attracted to the
positive charges in the ground?
 Why does the ground below have positive
charges?

Electricity that moves…
 Current:
The flow of electrons
from one place to another.
 Measured in amperes (amps)
 Kinetic energy
How can we control currents?
 With
circuits.
 Circuit: is a path for the flow of
electrons. We use wires.
There are 2 types of currents:
Current (DC) – Where
electrons flow in the same
direction in a wire.
 Direct
There are 2 types of currents:
Current (AC) –
electrons flow in different
directions in a wire
 Alternating
There are 2 types of circuits:
 Series
Circuit: the components
are lined up along one path. If
the circuit is broken, all
components turn off.
Series Circuit
There are 2 types of circuits:
Circuit – there are several
branching paths to the
components. If the circuit is
broken at any one branch, only
the components on that branch
will turn off.
 Parallel
Parallel Circuit
Conductors vs. Insulators
– material through
which electric current flows easily.
 Conductors
– materials through
which electric current cannot
move.
 Insulators
Examples
 Conductors:
 Insulators:
 Metal
 Styrofoam
 Water
 Rubber
 Plastic
 Paper
Activity Identifying
Conductors and Insulators
Page 208
What is Resistance?
 The
opposition to the flow of an
electric current, producing heat.
 The greater the resistance, the
less current gets through.
 Good conductors have low
resistance.
 Measured in ohms.
What Influences Resistance?
of wire – aluminum and
copper have low resistance
 Thickness – the thicker the wire the
lower the resistance
 Length – shorter wire has lower
resistance
 Temperature – lower temperature has
lower resistance
 Material
What is Voltage?
 The
measure of energy given to
the charge flowing in a circuit.
 The greater the voltage, the
greater the force or “pressure”
that drives the charge through the
circuit.
Difference b/t Volts and Amps
 Example
 Amps
– you could say that…
measure how much water
comes out of a hose.
 Volts measure how hard the water
comes out of a hose.
Ohm’s Law
 Resistance
 Ohms
= Voltage / Current
= Volts / Amps
What is an electromagnet?
– a magnet made
from a current bearing coil of wire
wrapped around an iron or steel
core.
 Electromagnet
What is a generator?
– a machine that
changes mechanical energy to
electrical energy
 Usually use moving magnets to
create currents in coils of wire.
 Generator
What is a motor?
– a device that changes
electrical energy to mechanical
energy that can do work.
 Motor
Creating Electromagnets Lab
Practice with Ohm’s Law
Ohms
4
15
2
9
6
Volts
100
150
30
45
48
Amps
25
10
15
5
8