Transcript Science

Voltage in
Electrical
Systems
Unit 4 Voltage Pages 71-76
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Voltage source  Primary cells
Conductors
 Secondary cells
Control element
 Electrode
Electrical appliance  Cathode
Electrical loads
 Anode
Electrical circuit
 In series
Direct current
 Electron
Alternating current  Frequency
Volts
 Voltmeter
Unit 4 Voltage
Pages 77
 Answer # 1-8
Electrical Systems
 Made up of voltage
sources, conductors,
control elements, and
appliances and machines
 Batteries/generators,
wire/circuits, switches,
lights/appliance
Conductor
 Any material that allows
the movement of
electrical energy
through it
Control Element
 Wall switch
 Volume on a radio
 Variable speed switch
Electrical Load
 Motor
 Light Bulb
 Appliance
Electrical Circuit
 Closed path made by
connecting voltage
sources, control
elements, and electrical
loads
AC vs. DC Electricity
 AC – Alternating Current
 DC – Direct Current
AC
 Electric charges move
back and forth many
times a second in the
wire
DC
 Electric charges in wires
always move in one direction
AC
 Produced by alternators
DC
 Produced by batteries
Dry-cell batteries
 A chemical produces the voltage
Wet-cell batteries
 Contain a liquid electrolyte
 Usually a strong acid
 Used to start engines because
they can deliver a lot of power
 The ability to recharge a
battery allows us to group
these chemical producers of
voltage into two classes
Primary
cells
 Not
easily
recharged
Secondary
cells
 Easily
recharged
How are DC Voltage
sources connected?
 The output of a voltage source
comes from two terminals
called electrodes
 DC sources normally have two
electrodes
 A Positive and a negative
How are DC Voltage sources connected?
 Electrons move in the circuit as
if they were flowing out of the
negative electrode and into the
positive
 The negative electrode is called
the “cathode”
 The positive electrode is called
the “anode”
How do we produce higher voltage?
 DC voltage sources can be
added together in series
 Positive source must be
connected to the negative
terminal of the other source in
succession
 If connected in an opposing
manner it will sometimes
cause battery damage
What makes up a simple DC Circuit?
 How do we make schematics?
 Symbols:
 Battery
 Light bulb
 Switch
 Conductors
AC Voltage
 AC Voltage changes direction
about 60 times each second
 This rate of change is called
the frequency
 Frequency is measured in
cycles per second or hertz
How do we measure voltage
 Modern electronics have made
digital voltmeters available
 Oscilloscopes are used often in
analyzing, testing, and
troubleshooting electrical
systems and circuits
 They can also be used as
voltmeters