Download Electricity

Electricity Unit Overview
Wednesday, April 1, 2015
Unit 9: Electricity
Wednesday, 4/1
 Take out your notes and retrieve a calculator for you open note quiz.
Upcoming dates:
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Monday, 3/30 – Wednesday, 4/1 –arena scheduling window
Monday, 3/30 – delayed start; 1st and 3rd periods only
Monday, 3/30 – Wednesday, 4/1 –arena scheduling window
Wednesday, 4/1 – delayed start; 2nd and 4th periods only
Thursday, 4/2 – 5SW extra credit due by 4:30
Tuesday, 4/7 – open note quiz (DATE CHANGE)
Tuesday, 4/7 – last day to turn in missing electricity assignments
Thursday, 4/9 – Electricity test (grade will go on the 6SW)
Friday, 4/10 – End of 5SW
Quiz
Motion
of free
charges
No
motion
of free
charges
Unit Overview
Types of Electricity
Dynamic
Direct Current
(DC)
Series
Static
Alternating
Current (AC)
Parallel
Complex
Electric Current
 The continuous flow of electrons through a conducting
metal.
Alternating Current
 Flow of current that periodically changes direction
 Produced in power plants
 Current from a wall outlet changes direction 120 times
per second
Direct Current
 The flow of current in one consistent direction
 Examples
 Batteries
 Solar cells
 Current from a battery travels from the positive terminal to
the negative terminal.
Common Language
Note Taking Guide
Quantity
voltage
current
resistance
Symbol
Definition
Unit
Measuring
Device
Voltage
 Voltage (V) (also know as Potential Difference)
can be thought of as the force pushing electric
charges along a conductor. Voltage between two
points creates an electric field.
 Measured in Volts (V)
Voltmeter
a device that measures
electric potential difference,
must be connected in parallel
Current
 Electric current (I) is the movement of
electric charge in a conductor.
 Measured in Amps (A)
Ammeter
a device that measures current
attached in series
Resistance
 Resistance (R) is a measure of how difficult it is to
push the charges along.
 The energy is transformed at the resistor (potential
energy is converted).
 Examples: light bulb, charging your phone, making
coffee, etc.
 Measured in Ohms ()
Note Taking Guide
Quantity
Symbol
Definition
Unit
Measuring
Device
voltage
V
Energy in the circuit
Volts
Voltmeter
current
I
Rate of flow
Amps
Ammeter
resistance
R
Opposes current
OhmsΩ
Ohmmeter
Measuring voltage and
Resistance
 On the back table there are circuit boards and multimeters (you can use as a voltmeter and an ohmmeter.
Directions
 Part 1
 Measure the voltage of the battery
 Turn the dial to 20 on the multi-meter (top left)
 Place one probe on the positive (+) end and one probe on the
negative (-) end.
 Record the voltage
 Part 2
 Measure the resistance of the resistors
 Turn the dial to 200 (bottom left)
 Place a probe on each side of the resistor
 Record the resistance for each resistor (green, blue, and red)
 Part 3
 Using the items in your box create a circuit that will illuminate a
bulb.
Ohm’s Law
 Ohm's Law deals with the relationship between voltage and
current in an ideal conductor.
 Ohm's Law is given by:
V = I * R
Example
A flashlight that is powered by 3 volts and uses a bulb
with a resistance of 60 ohms. What is the current flowing
through the circuit?
Electrical Circuit Terminology
 Circuit – a path that allows electricity to flow
 Circuit diagram – a simplified representation of an
electrical circuit that shows only the electrical
connections of elements in a circuit.
 Complete circuit – a circuit with an unbroken path that
allows electrons to flow.
 We will study two types of circuits:
 Series circuit
 Parallel circuit
Practice
Unit Overview
Types of Electricity
Dynamic
Direct Current
(DC)
Series
Static
Alternating
Current (AC)
Parallel
Complex
Series Circuits
Resistors can be connected in series; that is, the current
flows through them one after another
.
Kirchhoff’s Rules
Loop Rule: The sum of the potential differences
(voltage) around any closed circuit loop is zero.
Series
Resistor Circuits
1. total resistance is the sum of the
separate resistors
RT = R1 + R2 + R3 + ...
2. current is the same through each resistor
IT = I1 = I2 = I3 = ...
3. total potential difference is the sum of each
VT = V1 + V2 + V3 + ...
In other words, in a series circuit,
resistance and voltage add,
but current stays the same.
Series Circuit Example