Download Voltage in Electrical Systems

1.3.2
 Define electric potential, or voltage.
 Differentiate between AC and DC.
 Identify the most common source of DC voltage.
 Describe how to connect DC voltage sources so that
voltage will be added.
 Recall that a field is a model used to help
understand and predict how forces are transmitted
from one object to another.
 Electric field – electric force per unit charge.
FE
E
q
Unit is Newton per
Coulomb (N/C)
Click on this link to go to an electric field simulation from Phet
 Potential energy – energy of a particle associated with
its position.
 When charges are within an electric field an electrical
potential difference is created.
 Volt – unit of measurement for potential difference.
(electrical potential, voltage)
 Voltage is the prime mover in electrical systems (like
pressure in fluid system).
Gravitational potential
difference – ability to accelerate
a mass between two heights.
GPE = mgh
Units: N•m, or J
Electric potential difference (or
voltage) – ability to accelerate
an electric charge between two
points in an electric field.
V = E  d
Units: N•m/C, or J/C (or Volt, V)
Flow caused by “potential” difference
Fluid system
Electrical system
Current – Flow
Recall, pressure is a prime mover in fluid sytems.
Voltage is a prime mover in electrical systems.
The flow of charge is called current. Current continues until the
plates are neutral.
 Pump is used to
maintain pressure
difference.
 A battery is used to
maintain a potential
difference.
 Voltage source (battery or generator)
 Conductors (wires or circuit board)
 Load (motor, lights, etc.)
 Control element (switch)
Electrical
circuit
Control
Voltage
source
Electrical
Load
 Load – an appliance or machine.
 Conductor – material through which charge can easily
flow.
 Control element – a switch that turns the current in the
system on or off.
 Electrical circuit – closed path for current flow created by
connecting voltage sources, conductors, control elements,
and loads.
Electrical
circuit
Control
Voltage
source
Electrical
Load
 Two types of current (or charge) in electrical
systems:
 Direct current (DC) – current flows in one direction.
 Produced by batteries
 Alternating current (AC) – current flows back and
forth many time each second.
 Produced by alternators
 Direct Current (DC) – charge flows in one direction.
 Batteries
 Solar Panels
 Alternating Current (AC) – charge flows back and
forth.
 Alternators
 Generators
 Cell – single unit that houses on or more chemicals.
 Electrons and ions are separated in a cell creating a
voltage.
 Voltage depends on the chemicals used (Table 1.6).
 Battery – a collection of two or more cells
connected together.
 Battery is “dead” when voltage drops below that
required to drive the load.
 Types of cells (Figure 1.38)
 Primary cell – one-time use.
 Secondary cell – rechargeable.
 Can be added by connecting cells in series, connecting
the positive terminal from one cell to the negative
terminal of the next cell.
 Individual voltages of each cell adds together (Figure
1.39).
 In the circuit, electrons move out of the negative
terminal/electrode (or cathode) and enter the positive
electrode (or anode)
 Wire
 Switch
 Lamp
 Load
 Battery
 AC power
Use this Phet web site link for DC Circuit Construction
to download and practice making DC circuits.
Click on this Phet web site link for DC Circuit Lab to
get more practice with DC circuits
 Positive and negative terminals change many times
per second.
 Majority at a rate of 60 cycles per second
 Cycling rate, called frequency.
 Measured in hertz, cycles per second (1/s, or Hz).
AC Circuit Demonstration
Click on this Phet web link on AC Current – click on the link,
download the program and practice making AC circuits
Click on this Phet web link for the AC Current Lab simulation.
 Electric field
Electrical force
Unit is Newton per Coulomb
(N/C)
•SI unit for charge is the Coulomb (C).
•Elementary charge of one electron or proton
is
1.60 x 10-19 C
•q1 and q2 are the charges on two objects.
•d = distance between charged objects
•K = constant = 9.0 x 109 N•m2/C2
Voltage
V=Exd
Electric field
E = V/d
E = electric field
d = distance
Unit is volts
Unit is V/m
distance
d = V/E
Unit is meters
Net Voltage
Vnet = Vf – Vi
Charge
# of electrons x elementary charge
1 electron
Unit is Coloumb
Direct current
Total voltage is the sum of all voltage sources
Vt = V1 + V2 + V3….
Battery + battery + battery – conductor (wire) – load – wire
.
Alternating current
Total voltage is difference between the voltage sources on each side
of the load.
Vt = V on side one – V on side 2
Battery – conductor – load – battery in reversed position - conductor
 Wire
 Load
 Switch
 Battery
 Lamp
 AC power