Introduction to circuits

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 has 3 main components:
 power supply – that create current;
 connecting wires – that allow current
to travel & return to the power source;
 various elements - that use the
current.

3. Common Electric Symbols
 Battery or
Power Source
 Bulb
 Wires
 Buzzer

4. Common symbols (cont’d)
 Switch
 Push-button
Switch
 Resistor
 Voltmeter
 Ammeter
V
A

5. Circuits
Power Supply
Resistor
A
Ammeter
v
Voltmeter
Light Bulb
Switch

6. Types of Circuits:
 There are 2 types of circuits:
 1. Series Circuit
 2. Parallel Circuit
SERIES
Trick to help identify type of circuit:
Series:Pen follows wire
Parallel: Pen can go in more than one direction
PARALLEL

7. Series or Parallel?
A
A
SERIES
SERIES
PARALLEL
PARALLEL1.
4.3.
2.

8.  Resistance, current intensity &
potential difference are all related.
 Formula:
Important Formula to Solve Circuits!!!
I
V
1
R
=
Resistance
Current Intensity
Potential
Difference
VERY IMPORTANT!!!

9. KEY POINTS
 Cross multiplication
(friend x friend ÷ foe)
 Formula R V
=
1 I

10. A circuit has a resistance of 10Ω & a
current intensity of 5A. What is the
potential difference?
R = 10 Ω
V = ? V
I = 5 A
10 = ?
1 5
V = 50V
R = V
1 I

11. A circuit has a resistance of 20Ω & a
potential difference of 100V. What is the
current intensity?
R = 20 Ω
V = 100 V
I = ? A
20 = 100
1 ?
I= 5 A
R = V
1 I

12. A circuit has a potential difference of 16V
& a current intensity of 2A. What is the
resistance?
R = ? Ω
V = 16 V
I = 2 A
? = 16
1 2
R= 8 Ω
R = V
1 I

13. 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.

14. Math – Cross Multiplication
Ex. 10 = x
1 2
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 x 2 ÷ 1 = 20
Diagonal to each other
“Friend times friend”
“Left-out”
“Divided by Foe”

15. 4
8
6
=
x
x
10
2
5
=
3
6
x
8
=
7
10
x
=
1.
2.
3.
4.
6 x 8 ÷ 4 = 12
10 x 2 ÷ 5 = 4
8 x 3 ÷ 6 = 4
10 x 7 ÷ 1 = 70
Sneaky one….anything by itself is considered
to be over 1
71
10 x
=

 
REMEMBER
Friend x Friend ÷ Foe