Download Chapter 35 Electric Circuits

Chapter 35
Electric Circuits
Interpret circuit diagrams.
Determine the equivalent resistance of
circuits having two or more resistors.
Explain the cause and prevention of
overloading household circuits.
Two Types of Circuits
• 1. Series Circuit
• 2. Parallel Circuit
Series Circuit
• In a series circuit, the current can only
take one path.
• All the current flows through every part of
the circuit.
– Christmas Lights – if you remove one bulb and
the whole strand goes out, then they were
made in series.
Series Circuit
Only one path to follow!
Parallel Circuits
• In parallel circuits,
the current can take
more than one
path.
–The electrical circuits
in homes and
buildings are parallel
circuits
Parallel Circuit
MORE than one path to follow (THREE)!
Ohm’s Law
• Ohm’s Law states that the current of a
circuit is the ratio of the voltage and the
resistance of the circuit.
•I=V/R
– I = current (amps)
– V = voltage (volts)
– R = resistance (ohms)
V
I
R
2009 Grade 10
Current
• Current is the flow of electrical
charges.
• Current is measured in amperes.
Resistance
•Resistance (R) is a measure of
how difficult it is for the charges
to flow through the wire.
Ohm’s Law
• Ohm’s Law states that the current of a
circuit is the ratio of the voltage and the
resistance of the circuit.
•I=V/R
– I = current (amps)
– V = voltage (volts)
– R = resistance (ohms)
V
I
R
Practice Problem
In this circuit, how
much current flows
through the light
bulb?
A
B
C
D
0.75 amp
1.50 amps
2.0 amps
3.0 amps
Current = voltage = V
resistance
R
Current = 1.5 volts = 0.75 amp
2.0 ohms
Voltage = Current x Resistance
9V = Amperes x 6 ohms or 9V/6ohms =
•
a.
b.
c.
d.
A 9 V battery is connected to a 6
Ohm resistor. How much current
will flow through the circuit?
54 Amperes
15 Amperes
3 Amperes
1.5 Amperes
14
15
16
17
18
19
20
21
22
23
24
Home
Which circuit is
built so that if one
lightbulb goes out,
the other three
lightbulbs will
continue to glow?
The other three bulbs will continue to glow.
This is a parallel circuit.
F, G, H above are series circuits.
If this
one
goes
out
The
Home
others
go
out.
If this
one
goes
out
54
Home
Home
Which switch, if opened,
will cause the light bulb to
stop glowing?
FQ
GR
HS
JT
If R was opened/off,
If T was opened/off,
the electricity would still go
the electricity would still go
through S to the bulb.
through S to the bulb.
If S was opened/off,
the electricity would still go
through R and T to the bulb.
If Q was
opened/off,
Battery
the electricity would NOT
make it to the bulb.
32
Home
How much current is flowing through this
circuit?
A 0.32 A
B 3.1 A
C 4.0 A
D 12.5 A
Current = 4 ÷ 12.5
47
What is the current in a copper
wire
that
has
a
resistance
of
2
Frequency = voltage ÷ resistance(ohms)
? = 9is
÷ 2connected
ohms and
to a 9-volt electrical source?
Home
Current (frequency)
F 0.22 amp
G 4.5 amps
H 11.0 amps
J 18.0 amps
46
Electricity travels in circuits
• A circuit is a COMPLETE path through which
electricity travels.
• Example of a circuit is a toaster.
• The handle pushed down connects the circuit.
Parallel Circuits and Overloading
• Lines carrying an unsafe load will be
overload
– To prevent overloading, fuses or circuit
breakers are inserted in lines that provide
power. Excessive current will “blow out” the
fuse or “trip” the circuit breaker, stopping the
current to prevent a short circuit.
• Short circuits occur usually because of faulty wire
insulation.