Download Types of Electric Circuits Series Circuit Mini-Lab Mini-Lab

Schematic diagram:
• A diagram of an electric circuit
• Straight Lines Only!
Schematic Diagrams Symbols:
Battery
Open Switch
Resistor
Closed Switch
Bulb
Types of Electric Circuits
Series Circuit
2 types of electric circuits:
Series Circuits
and
Parallel Circuits
More than one
path possible
for electrons to
flow
A single
path for
electrons to
flow
Total resistance = sum of the
individual resistances (light
bulbs) on the circuit path.
If one bulb burns out,
the whole strand of lights won’t work!
Mini-Lab
Make a circuit with two bulbs in series.
Done? Have a seat and continue to
work on the reading assignment.
Mini-Lab
Add a switch to your last circuit that can turn
both bulbs on and off.
Done? Have a seat and continue to
work on the reading assignment.
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Mini-Lab
Parallel Circuit
Make a circuit with two bulbs in parallel.
Done? Have a seat and continue to
work on the reading assignment.
Mini-Lab
Mini-Lab
Add a switch to your last circuit that can turn
one bulb on and off without affecting the
other.
Add another switch to your last circuit so that
the other bulb can be turned on and off also,
without affecting the other. s
Done? Have a seat and continue to
work on the reading assignment.
Done? Have a seat and continue to
work on the reading assignment.
An Analogy for a Circuit:
Voltage, Current and
Resistance
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VOLTAGE
(V)
is
ELECTRICAL POTENTIAL ENERGY
and is measured in
VOLTS (V)
Low Voltage
(Low Potential Difference)
Voltage can describe the
energy stored in batteries:
High Voltage
(High Potential Difference)
Anatomy of a Battery
Positive Terminal
Zinc Anode (-)
Graphite Cathode (+)
Chemical Paste
(makes the electrons)
Negative Terminal
About Batteries:
How does a battery work?
Electrons collect on the negative
terminal of the battery. If you connect a
wire between the negative and positive
terminals, the electrons will flow from
the negative to the positive terminal
as fast as they can.
About Batteries:
Where does a battery get its electrons?
Inside the battery itself, a chemical
reaction produces the electrons.
The speed of electron production
by this chemical reaction controls how
many electrons can flow between the
terminals.
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CURRENT (I)
CURRENT
(I)
ELECTRIC CURRENT is
the FLOW of electrons,
measured in
AMPERES (A)
What’s difference between…
Current I
Voltage V
(in Amperes)
(in Volts)
measures the flow of charge
1 AMPERE of Current
Means 1 Coulomb per second
6,250,000,000,000,000,000
electrons per second!!
RESISTANCE
R
you could say that…
Volts
measure the
pressure in
the hose.
Amps
measure how
much water
comes out of a
hose per second.
Resistance
Think of water
flowing through
a pipe. A narrow
pipe has more
resistance
because of it
slows the flow of
water through
the pipe.
ELECTRICAL RESISTANCE
slows down the current
and is measured in
OHMS ()
Conductors vs. Insulators
•Conductors – material
through which electric
current flows easily;
they have low
resistance.
Insulators – materials
through which electric
current cannot move;
they are resistors.
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Ohm’s Law
V = IR
Examples
V
Relates:
I R
Voltage (V) in volts (V)
Problem 1: A stove is connected to a 180-V outlet. If
the heating element has a resistance of 18 calculate
the current flowing through it.
V = IR
Given:
I = V/R
V = 180 V
I=?
R = 18 
Current (I) in amperes (A)
Formula:
I=V
R
I = 180 V

I = 10 A
Resistance (R) in ohms ()
R = V/I
Therefore, the current flowing through the stove is 10 A
Examples
Examples
Problem 2: In order to operate a hairdryer, the current
required is 2.5 A. What is its resistance if the voltage
supplied is 120 V?
Formula:
Problem 3: If the resistance of fridge is 130 and the
current is 0.845 A, what is the voltage?
Given:
V = 120 V
I = 2.5 A
R=?
R=V
I
R = 120 V
2.5 A
R = 48 
Therefore, the resistance of the hairdryer is 48 
Question # 1
A light bulb supplied
with a voltage of 36 V
has a 6 A current
flowing through it.
Calculate the
resistance of the light
bulb.
Given:
V=?
I = 8.45 A
R = 13.0 
Formula:
V=IxR
V = 8.45 A x 13.0 
V = 109.85 V
Therefore, the voltage of the fridge is 109.85 V
Question #2
A light bulb has a
resistance of 3 . What
is the current in the
light bulb when a
voltage of 12 V is
supplied?
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Electric Power Formula
P = IV
Electric Power (P)
P  IV
Relates:
Power = Current x Voltage
POWER IS MEASURED
IN WATTS
Remember, a Watt is defined as a Joule per second
1 W = 1 J/s
I V
Voltage (V) in volts (V)
P=IV
Current (I) in amperes (A)
V=P/I
Power (P) in watts (W)
I=P/V
Electric Energy (E)
Conversions
E  Pt
Electrical Energy = Power x Time
WHERE:
ELECTRICAL ENERGY IS MEASURED IN kilowatt-hours
POWER
IS MEASURED IN kilowatts
TIME
IS MEASURED IN hours
P
(kW·hr)
(kW)
(hr)
• To convert from Watts (Joules per second)
to kilowatts (kW), simply divide by 1000!
• To convert from kW to kW·hr, simply
multiply kW by the number of hours!
NOTE:
Example
*The kilowatt-hr (kWhr) is a measure of ENERGY, not power!
Power = Work / Time,
so
Power x Time = Work (Energy)
Problem 3: Remember our fridge?
Given:
V = 109.85
I = 8.45 A
R = 13.0 
This meter measures the amount of electric work done
in the circuits, usually over a time period of a month. The
work is measured in kWhr.
1.
How much power does the fridge use?
2.
If it runs 10 hours per day, how many kW·hr will be used
per month? (assume 1 month = 30 days)
3.
How much will it cost (assume 1 kWhr = 10 cents)
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END
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