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Chapter 13: Electrical Systems (13.1)

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Dunearn Secondary School Science Department

on 25 August 2014

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Transcript of Chapter 13: Electrical Systems (13.1)

(A)Electrical Current
Conventional Current
Definition: is when positive
charges flow from the positive
to negative terminal.
Definition: Electrical current is define as the rate of flow of electric charges.
SI unit : Ampere (A)
This 'topic' include
->1) Conventional current 3)Measuring current
->2) Electron flow 4)Effect of electrical current
Voltage/Potential different
Definition: Energy needed by a charge to move from one point to another in a circuit is known as potential difference or voltage.
1) SI unit: (V) (volts)
In series circuit
Vtotal
V2+V3=V1 OR Vtotal
Parallel Circuit
Potential differnce : V1 OR Vtotal=V2=V3
Vtotal
C) VOLTAGE
D)RESISTANCE
Definition: Resistance(R) of an electrical component is defined as the ratio of voltage across the component to the electrical current following through it .
SI unit : Ohm
Type of resistor
How resistance is affected in different circuit
Parallel
Series
Fix resistor
Rheostat
Chapter 18:Electricity
B) Electrical Current
C) Voltage
D) Resistance
A resistor having a definite resistance
An instrument used to control a current by varying the resistance.
Rtotal=R1+R2+R3+R4
V total/I total= V1/I1+V2/I2+V3/I3+V4/I4
/ = divide
Cannot sum the total resistance in a parallel circuit.
Rtotal = Vtotal/I total
Voltage
current

A) Circuit
-Definition: A series circuit is one that connects an electric source with its components one after the other, forming a single loop, providing only one path for the current to flow.
-Definition: A parallel circuit is one that splits into two or more branches, provide two or more different paths for the current to flow.
SERIES CIRCUIT
PARALLEL CIRCUIT
A) CIRCUIT
Resistance =
Electron flows
Measuring electric current with a ammeter
Ammeter MUST be connected
in series with the electrical
appliance ( in this case, the
light bulb) in order to get
Effect of
electrical
current
Heating effect
Chemical effect (electroplating)
magnetic effect
Behavior of current,voltage and resistance
Circuit symbols
Power supply
Galvanometer
Wire
All these heating appliances contain
coils of high resistance wire
When electric charges move through a high resistance wire, some of the electrical energy is transferred to atoms in the wire
When the atom receive the energy, the atom vibrates more and the wire is heated up
application in real life
When temperature rises above the surrounding temperature, heats is given out
Special thanks to:
Michael
(c4science)
Special thanks to: MarshallBrain.com/science
B)Electrical Current
Definition: is when the electron flows from the negative terminal to the positive terminal
This 'topic' include: 1) Series circuit 3)measuring voltage
2) Parallel Circuit
Series
Parallel
Current
Voltage
Resistance
ITotal = I1 = I2 = I3
Current remain the same throughout
the series circuit.
Vtotal = V1 + V2 + V3
Voltage is split up into the electrical
appliances in the series circuit.
Rtotal = R1 + R2 + R3
Resistance is split up among all the
resistor in series circuit. (If we are
Itotal = I1 + I2 + I3
Vtotal = V1 = V2 = V3
Vtotal
Itotal
Rtotal =
Current is split up into all the different branches in the parallel circuit.
Voltage remain the same throughout
the parallel circuit.
Special thanks to: Derek Owens
Electrical resistivity as a property of matter. The concept is explained, the equation is derived, and an example problem is solved.
Resistivity
R= resistance
P (rho) = resistivity
L= Length
A= Cross sectional area
Rho=resistivity of a material ,which means , how well a material resists or conduct an electric current.
Today topic will be on...
Electrical
current
Voltage
Circuit
Series
Circuit
Parallel
Circuit
Circuit
symbols
Conventional current
AND
Electron flow
How to
measure current?
Effect of
electrical current
Series
circuit
Parallel
circuit
How to
measure voltage?
ELECTRICITY
Measuring voltage
Today we will be covering...
CHAPTER 18
-Advantages: By adding more power source (like batteries) it can increase the output energy -> Higher voltage across the electrical appliances
-Disadvantages:It is impossible to control the electrical appliances individually.
-Advantages: If one of the electrical appliances blows, the circuit will still be a close circuit.
Having multiple power sources will not increase the voltage across the electrical appliances in the circuit.
The next concept is something out of our syllables...
You may not understand. :)
Voltmeter MUST be connected in parallel with the electrical appliance ( in this case, the light bulb) in order to get the correct reading.
voltmeter connected parallel to the light bulb
Notice something missing?
Resistance is missing!
To know what is resistance , you have to know voltage and current FIRST :)
Resistance
Type of resistor
How to calculate resistance
How resistance is affected in different circuits
A simple series circuit
If one of the bulb fuse, the circuit will break.
2 batteries
1 battery
Circuit 1 has more voltage across the lamp/bulb compare to circuit 2.
(taking that the batteries and the lamp/bulb are identical )
And
a simple parallel circuit
The brightness of the bulb will not be affected by the number of bulbs in the circuit.
Series circuit
Series circuit
Parallel circuit
Parallel circuit
or
Voltage :
When sum up the voltage across resistor 1 and 2 , it is equal to the voltage across the batteries.
resistor 1
resistor 2
the voltage is the same throughout the whole circuit. ( if the circuit is closed!)
Resistance
Sum all the resistance to find the total resistance. OR Find the individual resistance using R=V/I then sum them up.
when
resistance increase,
current decrease.
A short summery of the behavior of current, voltage and resistance :)
real life application for electroplating
Chemical effect (electrolysis)
Electrolysis is the process of passing electricity through the conducting solution to result in a chemical change
use to decompose compound into its constituent elements
Electrolysis of acidified water produces hydrogen and oxygen!
Resistor must be place in series with the electrical appliances!
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