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Potential difference and emf
The potential difference across the terminals of a battery when it is not in a complete circuit is the electromotive for
The potential difference across the terminals of a battery when it is in a complete circuit is the terminal potential dif
Voltage is a measure of the work required/done to move a certain amount of charge and is equivalent to J·C−1.
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Current
Current is the rate at which charge moves/flows and is measured in amperes (A) which is equivalent to C·s−1.
Conventional current flows from the positive terminal of a battery, through a circuit, to the negative terminal.
We use the symbol I to represent current. We can calculate current using:
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Measuring current and potential difference
Voltmeters measure potential difference (voltage) and must be connected in parallel.
Ammeters measure current and must be connected in series.
Photo by Ufbastel on wikipedia
Photo by Christos vittoratos on wikipedia
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Resistance
Resistance is a measure of how much work must be done for charge to flow through a circuit
element and is measured in ohms (Ω) and is equivalent to V·A−1.
Resistance of circuit elements is related to the material from which they are made as well as the physical characte
Photo by Oskay on Flickr
7. Resistors in series circuits
Current is constant through resistors in series and they are called voltage dividers as the sum of the voltages is equ
The total resistance of resistors in series is the sum of the individual resistances.
8. There are many circuits in which more than one device is connected to
a voltage source.
Series wiring means that the devices are connected in such a way
that there is the same electric current through each device.
11. Resistors in parallel circuits
Voltage is constant across resistors in parallel and they are called current divides because the sum of the current thro
The total resistance of resistors in parallel is calculated by using:
12. SERIES CIRCUIT:
-There is only ONE PATH for the electrons to
take between any two points in the circuit.
*There will be no alternative route.
-Has more than one RESISTOR. Since there is
only one path for the current to travel, the
current through each of the resistors is the
same.
*Resistors are components that are used to
control the amount of current flowing in a
circuit.
13. PARALLEL CIRCUITS:
-Two or more components are connected
between the same two points.
- Has more than one resistor and gets its name
form having multiple paths to move along.
* Charges can move through any of the
several paths. If one of the items in the circuit
is broken, then no charge will move through
that path. But other paths will continue to
have charges flow through them.
14. 20.7 Parallel Wiring
Parallel wiring means that the devices are
connected in such a way that the same
voltage is applied across each device.
When two resistors are connected in
parallel, each receives current from the
battery as if the other was not present.
Therefore the two resistors connected in
parallel draw more current than does either
resistor alone.
18. SERIES CIRCUIT PARALLEL CIRCUIT
DESCRIPTION If one the items in the
circuit is broken, then
no charge will move
through the circuit
because there is only
ONE PATH.
If one of the items in
the circuit is broken
then no charge will
move through that
path, but OTHER
PATHS will continue to
have charges flow
through them.
RESISTOR As more resistors are
added, the overall
current in the circuit
decreases.
As the number of
resistors increases, the
overall current also
increases.
RECAP!
19. EQUIVALENT RESISTANCE
-Is the amount of resistance that a single resistor would need in order to
equal the overall effect of the collection of resistors that are present in
the circuit.
RESISTORS IN SERIES:
Two resistances are connected in series if all the current from one
resistor must flow through the second; there is no alternative route.
20. Equivalent resistance:
From conservation of
charge:
I1 = I2 = I
where I is the current through the combination.
From conservation of
energy:
V1 + V2 = V
where V is the potential difference across both
resistors.
The two resistors can be replaced by a single resistor with the
equivalent resistance
For more than two resistors, Req = R1 + R2 + R3 + ...
21. RESISTORS IN PARALLEL:
- Two resistors are connected in parallel if they are joined at both ends
such that the potential difference across both resistors is the same. The
current splits, flows through the two resistors, then comes back together
with no alternate path.
22. Equivalent resistance:
From conservation
of charge:
I1 + I2 = I
From conservation
of energy:
V1 = V2 = V
The two resistors can be replaced by a single resistor with the equivalent
resistance Req:
For more than two resistors:
23. RECAP!
SERIES CIRCUIT PARALLEL CIRCUIT
The total resistance of the
circuit, also called effective
resistance is equal to the
sum of the individual
resistances.
The inverse of the total
resistance of the circuit, is
equal to the sum of the
inverses of the individual
resistances.
R = R1 + R2 + R3 + … 1/R = 1/R1 + 1/R2 + 1/R3
+ …
24. ELECTRIC POWER AND ENERGY
Electric Power:
- Represents the rate at which energy is converted from the electrical
energy of the moving charges to some other form.
- The SI unit of power is watt.
Electric Energy:
-Represents the presence and flow of an electric charge. The energy
portion of electricity is found in a variety of phenomena such as static
electricity, electromagnetic fields and lightning.
-Consumption of electrical energy is measured by Watt x Hour (Wxh)
* 1Wh = 3600 joule = 859.8 calorie
25. REFERENCES
• The slides were compiled by Mesolo MP with the slides from slide
share, the authours and links are:
• http://www.slideshare.net/fourangela/series-parallel-11767502?qid=2fc1a7d9-1e75-4571-ab7f-5a3d8c903066&v=qf1&b=&from_search=9
• http://www.slideshare.net/Siyavula_Education/electric-circuits-grade-10
• http://www.slideshare.net/wsautter/electrical-circuits.Nisa Sho on Dec 31, 2008
• http://www.slideshare.net/Wansyi/electricityelectronics-ch20-presentation. Walt Sautter, retired at Middlesex County College on Feb
12, 2010
