Download Voltage (PP) - Instructure

EE1010
Laboratory Instruments and Methods
Lee
Brinton
801-957-4828
James Quebbeman 801-957-4786
Harvey Wilson
801-957-4786
Four Fundamental Forces
of Nature
Strong Nuclear Force: Binds positively charged protons and neutrons
together to form the nucleus – strongest of four forces.
Electromagnetic Force: Attraction and repulsion of charged particles.
Weak Nuclear Force: Associated with Beta decay, holds an electron and
proton together to form neutron in nucleus of atom.
Gravitational Force: Attractive force of mass – weakest of the forces.
Gravitational Field
Directed Towards the Mass
A gravitational field has the potential to create a force when
another mass is brought into the reach of the field.
Force Due to Gravitational Field
m
F = mg
Δw = energy = Fd
= mgh
Potential = gh
Everything Is Made Of Atoms
Nucleus
Protons
Neutron
-
BIG!
1,000’s of times
BIGGER than
electrons
+
+
Surrounding the Nucleus
-
Electrons Teeny, tiny, itsy, bitsy
Electrons:
Like flies buzzing around a cow!
Moooooove,
You pesky
Flies!
Electrical Field
Charged Particles Produce Fields Analogous to Gravitation Field of a Mass
E
-
Force Due to Electrical Field
d
E
+
Attractive
Force
Force:
F = qE
similar to
Energy : Δw = Fd = qEd
Potential: V = qEd/q = Ed
F = mg
Δw = mgh
mgh/m = gh
In Electricity, this last quantity is called Voltage or Electromotive Force
For an introduction to Voltage titled
“Physics – What is Voltage”
go to this web site:
http://www.youtube.com/watch?v=wT9AsY79f1k&list=PL752E6CC30238E56A&index=1
Voltage Generation
These voltages can be produced (generated) in a number of different methods
• Chemically
• in a battery (or a potato)
• in a solar cell
• in a hydrogen fuel cell
• Mechanically – Generator turned by a mechanical device like
• a steam powered turbine
• a hydro powered turbine
• a wind mill
Regardless of how the voltage is generated, a voltage source has two terminals
– one terminal raised to a higher voltage than the other by one of the methods
mentioned above. Schematically, voltage sources are represented with one of
the following symbols:
+
+
-
A DC voltage source symbolic
of separated metallic plates in a
battery
A generic voltage source that can represent
either a DC or AC voltage.
Potential or Voltage
Always Relative to a Reference
For example, in a 9 Volt battery, the chemical reactions raise the“+” terminal
to a potential 9 volts higher than the negative terminal
+
9V
-
This terminal is 9 V.
higher than …
this terminal.
Reference Voltage
The voltage at a point is always measured relative to some other
point. In a 9 V battery, the “+” terminal is said to have a voltage that
is 9 Volts higher than the “-” terminal. It becomes useful to define
one point within the circuit as the reference voltage (call it 0 Volts)
and compare the voltage of all other points in the circuit to that.
In hand held or battery operated devices, the
reference point of the circuit is frequently the
negative terminal of the battery.
In devices powered by the utility grid, the reference
point of the circuit is usually the neutral wire which
is usually connected to the earth ground. Modern
construction codes direct that this connection to the
earth is made by driving a copper rod into the
ground.
Current – Rate of Flow
Water Flows From
Higher to Lower Elevation
+
Gallons per Minute
Charged Particles Flow
Higher to Lower Voltage
Coulombs per Second
Amperes
Electrons Constrained Within a Conductor
With the “+” terminal at a higher voltage than the “-” terminal, a
potential exists to force positively charged particles from the
higher voltage to the lower voltage. To accomplish this, a charge
carrying material known as a conductor must be connected
between the terminals to provide a path for the particles to flow.
This closed path is referred to as a CIRCUIT. The flow of
charged particles is referred to as a CURRENT.
+
+
-
A circuit schematic showing a battery (left) connected
using conductors (red lines) to a resistor (right) .
Historical Note
When we talk about current, we refer to it as
though “+” charges flow from the “+”
terminal to the negative terminal. This is
the commonly used convention we use.
+
+
-
-
In reality, electrons are flowing from the
negative terminal to the positive terminal.
Another Analogy
Pressurized Water in a Closed Pipe
Pump
infuses
energy by
raising
pressure
X
Restriction
reduces
pressure and
dissipates
energy
Battery
infuses
energy by
raising
voltage
Resistor
reduces
voltage and
dissipates
energy
Voltage and Elevation
(An Analogy)
Our understanding of voltage can be enhanced through a comparison to elevations. Elevations are always
measured relative to some reference elevation that is considered to have an elevation of 0 feet. Heights
above the reference are positive and heights below the reference are considered negative. For example, sea
level is frequently considered the reference elevation and assigned an elevation of 0 feet. Other elevations
are measured relative to sea level.
Highest point on Earth
Elevation of Mt. Everest 29,035 ft
Elevation of base station 17,600 ft
Sea Level = 0
The difference in elevation between the
peak and the base camp is
hpeak – hbase
or
29,035 – 17,600 = 11,435 ft.
When referring to the change in elevation,
we can either say there is an increase in
elevation of 11,435 ft from the base camp to
the peak or a drop in elevation of 11,435 ft
from the peak to the base.
The drop in elevation going from the peak of Everest to
the bottom of the Challenger Deep is:
hpeak – hdeep
or
Lowest point on Earth
29,035 – (-36,200) = 65,235 ft.
Challenger Deep – Marianas Trench
-36,200 ft
Voltage and Elevation
(An Analogy)
1 kΩ
+
1 Volt
-
1 Foot
+
10 Volts
-
10 kΩ
12 V
1 kΩ
Circuit schematic
12 Feet
10 Feet
+
1 Volt
-
1 Foot
Elevation chart
Schematic and Simulation
1 kΩ
+
1 Volt
+
10 Volts
-
10 kΩ
12 V
1 kΩ
+
1 Volt
-
Simulate using
Voltage_Ideal_Simulated.rtf
Measuring Voltage
 Construct the circuit in a simulator
 Measure and record each voltage in the table below
d
1 kΩ
12 V
+
1 Volt
c
10 kΩ
b
1 kΩ
+
10 Volts
+
1 Volt
a
VDA
VCA
VBA
VDC
VCB
VDB
Building Circuits – Another View
Two Versions of Prototype Boards in Our Lab
Protoboard description:
http://www.doctronics.co.uk/prototyp.htm#board
Resistor description:
http://www.youtube.com/watch?v=Gc1wVdbVI0E
Schematic and Protoboard
+
1 Volt
-
1 kΩ
12 V
10 kΩ
1 kΩ
+
10 Volts
-
+
1 Volt
-
Ohm Meter (verify resistance value)
Measure Resistance at One Point Relative to Another.
Indicated value should be within 5% of expected value.
Volt Meter
Measure Voltage at One Point Relative to Another.
Value indicated may be slightly different from expected.
Measuring Voltage
 Construct the circuit on a protoboard
 Make the same measurements that were done in the simulation
 Compare the ideal values with the simulated and the protoboard values
d
1 kΩ
12 V
+
1 Volt
c
10 kΩ
b
1 kΩ
+
10 Volts
+
1 Volt
a
VDA
VCA
VBA
VDC
VCB
VDB