Lesson 7: Circuits and
Current
Chapter 13.1 and 13.3 PP.551-4 AND 556-7
We are learning about series and parallel
circuits. We are learning about amperage
and how to connect an ammeter.
I will be successful when I can draw a
series and parallel circuit.
I will be successful when I can connect
(draw) an ammeter correctly to a circuit.
Review - What are the 4
main components of electric
circuits?
ELECTRIC
CIRCUITS
A continuous path in which electrons can
flow. A circuit has 4 main parts:
1. Conducting Wire
2. Source
3. Switch
4. Load
1. Conducting Wire: A conductor that joins
the all parts of the circuit. Ex: Copper
wire.
Conducting
Wire
2. Source: A source of electrical energy. Ex:
battery.
Energy Source
Source of Electrical Energy: Includes things like batteries and variable DC
power sources.
● They provide energy to the circuit that allows electrons to flow.
_
+
Electric Cell
(Battery)
_
+
Three Cell
Battery
3.Switch: Controls the current flow in an electric
circuit by opening and closing
• Switch “on” circuit is closed
• Switch “off” circuit is open
Switches
Switch: A device that can turn a circuit on and off.
● They do this by either opening or closing the circuit.
Open Switch
Closed Switch
4. Load: Part of an electrical circuit that converts
electrical energy to other forms of energy.
I.e..) heaters, lamps, fans
A light bulb converts
electrical energy into light
energy and thermal
energy.
Let’s Play: Phet Circuit
BLM 12.2-1
Electrical Loads
Electrical Load: A device that changes electrical energy into some other kind of
energy.
● This process is called work.
M
Lamp
Electric
Motor
Discussion
Points
• How is a parallel circuit different from a
series circuit?
• What is an ampere?
Circuit
Diagrams
A way of drawing
an electrical circuit
using standard
symbols.
SERIES CIRCUIT
A circuit in which the loads are connected end to end so
that there is only one path for electrons to flow.
Practice building and
1. drawing
Build a series circuit that can turn two light bulbs on and
off.
• discuss with your group what components are required to
make this circuit work before building
2. In your notes, please draw this circuit using the correct
symbols for drawing circuits.
• Draw what the circuit would look like with the light OFF
• Draw what the circuit would look like with the light ON.
Please use the PhET Circuit Construction Kit to build.
PARALLEL CIRCUIT
A circuit in which the loads are connected by branches
so that there are 2 or more paths for electrons to flow.
Practice building and
1. drawing
Build a parallel circuit that can turn two light bulbs on
and off.
• discuss with your group what components are required to
make this circuit work before building
2. In your notes, please draw this circuit using the correct
symbols for drawing circuits.
• Draw what the circuit would look like with the light OFF
• Draw what the circuit would look like with the light ON.
• Show the two pathways that the current can travel in
two different colours.
We don’t have enough kits - if you feel like you aren’t able to
get your hands on the kit, please use the PhET Circuit
ELECTRIC
CURRENT
•Symbol for Current is I
•A measure of the rate of the electron flow past a given
point in a circuit; measured in amperes (A).
•Ammeter: A device used to measure electric
current. An ammeter must be connected in series
with the load to measure the current through the
load.
1 A = 1c/s
c=
Coulomb
Ammete
r
Practice building and
drawing
1. Build a series circuit with ONE battery and ONE light.
2.
3.
•
•
Include an ammeter in the circuit to measure the
electric current. Where should the ammeter go?
Write down the electric current measured from the
ammeter.
Add another light to the circuit, so that you now have a
total of two light bulbs.
BEFORE YOU BUILD, MAKE A PREDICTION: What do
you think will happen to the electric current (amperes)?
AFTER YOU BUILD: Why do you think this happened
to the current?
SAFETY WITH ELECTRIC
CURRENT
• 0.001 A : a tingling sensation.
• 0.05 – 0.1 A : cause muscles to convulse uncontrollably.
• 1.0-4.3 A : can stop your heart if it passes through your
chest.
• A typical Hong Kong circuit ≈ 6 A
• A typical Canadian circuit ≈ 15 A
Coulom
•bs
A Coulomb is a QUANTITY of electric charge.
•The movement of electric charge past a point is called
current in an electric circuit.
•For example a flashlight bulb that has a current of one
ampere will pass one coulomb of charge every second; so in
ten seconds, ten coulombs have passed through the lightbulb
1 A = 1c/s
c=
Coulomb
Calculating Current and
Charge
We can calculate the amount of current (I) flowing
through a circuit.
We can also calculate the quantity of electric charge (Q)
flowing through a circuit by rearranging the equation.
What equation would we use to solve for Q?
Practice
Questions
Current and Charge Calculations and Word
Problems
Textbook
• Page 554 Complete Questions: 1, 2, 5
• Page 557 Complete Questions 1, 2, 3, 4
Homework Answers
p.554
Homework Answers
p.557