Transcript V - Mr. B. Gillis`s Weblog

Mr. Gillis’ Science Class
What needs to
happen to get
the bulb to
light?



Connectors
Energy source
Control Device
 Ex. switch

Load
 Place the bulb in a socket




Use one D cell
Make the bulb light!
Add a switch to conserve D cell energy
Use your finger to trace the path of
electricity from one terminal of the D
cell to the other terminal




Wire
Bulb
Battery
Switch
Symbols used for
Diagramming


1. Static electricity is an electric charge that
remains in a fixed position or region on an
object. Current electricity is an electric charge
that is moving in one or more paths. The
moving electric charge is called an electric
current. The electric current may be flowing
in an uncontrolled path (lightning) or a
controlled path (electric circuit).
.
Part of the Circuit
Function
Examples
Source of electrical
energy
Provide energy to the
electric load in the
circuit
Battery, 120V source
Electric load
Convert electrical
energy into another
form of energy
Light bulb, motor
Electrical control
device
To control the flow of
electric current in the
circuit
Switch, fuse
Connectors
To provide a
conducting path
between the parts of a
circuit
Connecting wires,
copper strips
 3.
The electric charge flows from
the negative terminal of the dry cell
(yellow wire), through the switch,
the bulb and back to the positive
terminal of the dry cell (green wire).
Negative charges are released at
the negative terminal and are
attracted toward the positive
terminal.
ENERGY (E) – the ability to do work

There are many
forms of Energy
kinetic,
mechanical,
chemical,
solar...
POTENTIAL ENERGY
KINETIC ENERGY

Energy of motion
stored Energy
ex: spring, elastic band


When + and – charges
are pulled apart there
are attractive forces
wanting to put them
back together, this is a
form of potential
energy as it has the
ability to do work!
Stored electrical energy
such as that stored in a
battery


Converts:
Chemical Energy into
Electrical Energy
+ and – charges are
separated into terminals
located at either end of
the cell, when
connected – charges
(electrons) travel
towards the + (positive)
terminal as the –
charges repel one
another
 Batteries
have electric potential
Energy because the stored e-’s
have the ability to do work, i.e. run
your CD player!


different
electrodes (usually
metals also Carbon)
And an electrolyte
(electrolytic
solution)
Change in potential energy per
coulomb of charge
Measured in volts
voltmeter
(V) by a


1) a) The electrons must move
continuously around the circuit to
continually provide electrons from the
circuit to the positive terminal on the
dry cell for chemical reactions to occur
inside the dry cell.
b) The electrical charges flow from the
negative terminal of the dry cell into
the circuit. When the chemical
reactions occur inside the cell, the
electrons are released at the negative
terminal (electrode).



2) a) Electric potential (voltage) is the
energy each electron has as it leaves the
negative terminal of the dry cell.
b) The SI unit for electric potential (voltage)
is the volt, and the symbol for the volt is V.
3) When the dry cell is actually made, a
limited number of chemical reactions occur
that release electric charges that
accumulate on the negative terminal of the
dry cell.

The voltage of an electrical energy
source is a measure of the energy of the
individual electrons at the negative
terminal, compared to the positive
terminal. The voltage of the electrons at
the negative terminal of a 120-V source
is 20 times greater than that of electrons
at the negative terminal of a 6-V battery.
This extra amount of energy per electron
is sufficient to give someone a severe
electric shock.
4)
Stairs = the
voltage
 Backpack =
amount of
charge separated
 More work has
been done in B,
therefore it has a
greater Potential
Energy!

Electric Circuit
A complete
pathway that
allows electrons
to flow
 Transforms

electrical energy
into other forms
of Energy

Interactive website
Electric
Circuit
Analogy
Source – source of
electrical E
Switch – turn
circuit on or off
Interactive Website on
Conductor – wire
through which
current flows
Load – converts
electrical E into
other forms of E
•the
amount of charge passing a given
point in a conductor per second
•measured in amperes (A) by an
ammeter or (mA) by a galvanometer
Electrical Resistance:

Slows down the
flow of electrons
and transforms
electrical E into
other forms of E
E
Electrical

Light

Heat

Sound

Motion

etc
•Measured
•Equal
in ohms (Ω)
to the ratio of the voltage to the current
R = V/I
Current Dependent on
Potential (voltage)
Current Dependent on
Resistance
Factors
Affecting
the
1.
Length
2.
Diameter (thickness)
3.
Type of wire
4.
Temperature


Long, Thin
Tungsten wire
Short, Thick copper
wire
The Mathematical Relationship
comparing
voltage (V), current (I) and resistance (R)
V = I●R
Interactive website
V
I
R
Where:
V=I●R

I=V
R
R=V
I
V = voltage measured
in

volts (V)
I = current measured
in amperes (A)

R = resistance
measured
ohms (Ω)
in
Where:
V=I●R

I=V
R
R=V
I
V = voltage measured
in

volts (V)
I = current measured
in amperes (A)

R = resistance
measured
ohms (Ω)
in
STEP 1: Read and reread the question. Step up variables with known information.
V=?
I= 0.5A
R= 2Ω
Use a question mark for the unknown value you are trying to find. Be sure to include
units (V,A,Ω)
STEP 3: Convert units if necessary, measurements must be
in V for voltage, A for current and Ω for resistance. Fill in the
information given in the question (including units).
V =I●R
V = (0.5A)(2.0Ω)
V= 1.0 V
The flashlight would require a voltage of 1.0 V.
Used to control
CURRENT or
potential
difference
(VOLTAGE) in a
circuit




Add a second D cell to your circuit,
right next to the first. Be sure to match
up positive terminal with negative
terminal
Do you notice any difference?
Add a second light bulb to the circuit,
keeping only one pathway for electricity
to follow
What do you observe now?
Keep two D cells in the circuit
 Wire up the 2 light bulbs so that
there are two branches or
pathways for electricity to follow
 What differences do you observe?

Inverse Relationship
The amount of
potential energy
that each unit of
charge has
V
= voltage, measured in
volts
 I = current, measured in
amperes, or amp
 R = resistance, measured in
Ohms, symbol W

Battery by itself

Battery in a circuit

Current in a
circuit

Multimeter
completes
the circuit