1.
CIRCUITS
Objectives:
3.11 Analyze the distribution of current in various
combinations of circuit elements
3.12 Explain the distribution of electric potential in
various combinations of circuit elements
3.13 Explain the concept of electric potential
difference in circuits using an analogical model
3.14 to 3.18 Activities
2.
Circuits:
A circuit is made up of a power
supply, connecting wires &
various
elements
that
allow
current to leave a power source,
travel through the elements &
return back to the power source.
3.
Common Electric Symbols
Battery/Power
Source
Bulb
4.
Common symbols (cont’d)
Switch
Push-button
Switch
Resistor
Voltmeter
Ammeter
V
A
5.
Circuits
Power Supply
A
v
Ammeter
Resistor
Voltmeter
6.
Trick to help identify type of circuit:
Series:Pen follows wire
Types of Circuits: one direction
Parallel: Pen can go in more than
There are 2 types of circuits:
1.
2.
SERIES
Series Circuit
Parallel Circuit
PARALLEL
7.
Series or Parallel?
1.
2.
PARALLEL
SERIES
3.
4.
A
PARALLEL
SERIES
A
8.
Important Formula to Solve Circuits!!!
Resistance, current intensity &
potential difference are all related.
Formula:
Resistance
R V
=
1 I
Potential
Difference
Current Intensity
VERY IMPORTANT!!!
9.
Math – Cross Multiplication
Ex.
10 = x
1
2
Diagonal to each other
“Friend times friend”
“Left-out”
10 x 2 ÷ 1 = 20
“Divided by Foe”
x = 20
Always multiply the two numbers that are diagonal from
each other together.
Then divide by the “left-out” number
“Friend by friend divided by foe”
10.
REMEMBER
Friend x Friend ÷ Foe
x 8
=
1.
6 4
2.
3.
4.
6 x 8 ÷ 4 = 12
5 10
=
2 x
10 x 2 ÷ 5 = 4
8 6
=
x 3
8x3÷6=4
10 =
x
7
10 x
=
1 7
10 x 7 ÷ 1 = 12
Sneaky one….anything by itself is considered
to be over 1
11.
A circuit has a resistance of 10Ω & a
current intensity of 5A. What is the
potential difference?
R
1
R=
10 Ω
V=
?V
I=
5A
10
1
=
V
I
= ?
5
V = 50V
12.
A circuit has a resistance of 20Ω & a
potential difference of 100V. What is the
current intensity?
R
=
V
1
R=
20 Ω
V=
100 V
I=
?A
I
20
1
= 100
?
I= 5 A
13.
A circuit has a potential difference of 16V
& a current intensity of 2A. What is the
resistance?
R
1
R=
?Ω
V=
16 V
I=
2A
?
1
=
V
I
= 16
2
R= 8 Ω
14.
KEY POINTS
Cross
multiplication (friend x
friend ÷ foe)
V
Formula R
=
1
I
Helpful Summary Chart
SERIES
PARALLEL
SAME
DIFFERENT
Potential Difference
(V)
DIFFERENT
SAME
Resistance (R)
Req = R1 + R2 + R3
+…
1
1
1
1
=
+
+
Req R 1 R 2 R 3
Current (I)
15.
Electricity and Flowing Water
How and why electricity does what it does can be
explained by using a river as a comparison.
•The
water goes downstream because there
is a difference in altitude. This is the
same as potential difference where a
difference in charge exists between two
points in a circuit.
•The
quantity of water in a river can be
compared to the current. Lots of water,
large current. Little water, small current.
•Rocks
and boulders found in the stream
slow the flow of water. Resistors along
the circuit tend to slow the movement of
electrons.
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