Transcript Basic Electricity and Light Sensor

Basic Electricity and Potentiometer
Lesson 1
EET 1150
Cuyahoga Community College
Things you should know
• What is an atom?
The atom is the basic unit of all matter.
• Names the parts of an atom and their charges.
Protons (+), electrons (-) , and neutrons
repel
• Like charges ________
one another.
• Opposite charges ____
_____ one another.
attract
Current (A)
• Current is the flow of electrons
• Current is what flows through light bulbs to make
them light up light up and causes electronic
devices to operate.
• Units are in Amperes(A)
• Ampere is the measurement of electricity flowing
in a circuit.
What Cause Electron Flow?
The outer most shell is a called the
valence shell. The electrons on the
valence shell are called valence
electrons
The electrons on this shell are loosely
bound to the atom because they are far
away from the nucleus.
A electron from another atom can push
an valance electron from its obit and
takes it place.
When this process is continuously
repeated creates electron flow.
1 Ampere = 1 Coulomb of electricity flowing past a point in 1 second.
1A=1C/s
A coulomb is nothing more than a quantity of electrons
1 C = 6.25 x 10¹⁸ electrons= 6,250,000,000,000,000,000 electrons
If 3 C pass through this point in 2 seconds, how much current is
flowing? How many electrons are flowing past this point?
3 C ÷ 2 s = 1.5 A
Voltage (V)
Voltage is defined as the potential difference between two points
Voltage is as described as the pressure that forces
electrons through a path.
Never Ready
A battery is device that stores chemical energy and has an excess of
electrons on the negative terminal and a lack of electron on the positive
terminal
Electrons
Never Ready
Wire
Lamp
Resistance(Ω)
• Resistance is the opposition to current flow.
The water in these
tanks represents
current
The pipes provide the resistance
Tank 1
Tank 2
Which has tanks has the least opposition for water to flow out of the
tank?
Ohm’s Law
V stand for Voltage;
Units are in volts (V)
V
I
I stands for Current ;
Units are in amps (A)
R
R stand for
Resistance; units are
in ohms (Ω)
Ohm’s law states that current is directly proportional to voltage and inversely
proportional to resistance
Ohm’s Law
To determine voltage
To determine current
V
I
V=IxR
To determine resistance
V
R
I
V
R
I=V/R
I
R
R=V/I
Problem 1
Find the current running through this
circuit.
I=?
5V
5 volts/ 20 ohms = 0.25 A or 250 mA
+
-
R = 20 ohms or 20 Ω
Determine I if R = 40 Ω
5V ÷ 40 Ω = .125 A or 125mA
Determine I if R = 60 Ω
5V ÷ 60 Ω = .0833 A or 83.3mA
What happens to the current as the resistance increases and the
voltage is held constant?
Problem 2
Find Total Resistance = R₁ + R₂
Find Current in circuit
R₁
12V
R₁ + R₂ = 130 Ω + 50 Ω = 180 Ω
130Ω
+
12 V ÷ 180Ω = .067 A or 67 mA
R₂
50Ω
Determine I if V = 16V
Determine I if V = 20 V
16 V ÷ 180Ω = .089 A or 89 mA
20 V ÷ 180Ω = .111 A or 111 mA
What happens to the currents as the voltage changes and resistance is
held constant?
Problem 3
Find the voltage.
Find the resistance. Give answer
in engineering notation
R₁
V=?
3kΩ
+
I = 2m A
-
V = 24V
R =?
+
I = 0.02 A
-
3kΩ x 2mA = 6 V
24 V ÷ 0.02 A = 1200 Ω
3000Ω x .002 A = 6V
24 ÷ 20 mA = 1.2kΩ
3 x 10³ x 2 x 10 ̄ ³ = 6V
Power (W)
• Electrical Power is the rate at which electrical
energy is convert to another form of energy.
– A light bulb becomes hot after long use.
– sound from a speaker
– The movement of a robot from one side of a
room.
• The units for power is Watts (W).
Power
P stand for Power; Units
are in watts (W)
V stand for Voltage;
Units are in volts (V)
P=VxI
P
V
I
P = I² x R
I stands for Current ;
Units are in amps (A)
P = V² / R
Problem 4
Determine the Power.
I = .250 A or 250 mA
5V
+
R = 20 ohms or 20 Ω
-
P = 5 V x .250 A = 1.25 W
or
P = 5 V x 250 mA = 1250 mW
Potentiometer
• Variable resistor: changing the position of the
pot changes the resistance which changes the
voltage .
• Analog sensor with a range from 0 to 1015
• Turns 260 degrees
• Connected to an analog port
Potentiometer