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UNIT 1:
ELECTRICITY AND ELECTRONICS
(PART 2)
TECHNOLOGIES ESO 3
ELECTRICITY AND ELECTRONICS
4. TYPES OF CIRCUITS
4.1 SERIES CIRCUITS
4.2 PARALLEL CIRCUITS
4.3 MEASURING CURRENT AND VOLTAGE
4.4 MIXED CIRCUITS
5. TYPES OF CURRENT:
5.1 DIRECT CURRENT (DC)
5.2 ALTERNATING CURRENT (AC)
4. TYPES OF CIRCUITS
Components of an electrical circuit or electronic circuit can be
connected in many different ways. The two simplest of these are
called series and parallel and occur very frequently.
4.1 SERIES CIRCUITS
Components connected in series are connected along a single
path, so the same current flows through all of the components.
If you follow the circuit diagram from one side of the cell to the
other, you should pass through all the different components, one
after the other, without any branches.
4. TYPES OF CIRCUITS
4.1 SERIES CIRCUITS (continue)
In a series circuit, if a lamp breaks or a component is
disconnected, the circuit is broken and all the components stop
working.
If you put more lamps into a series circuit, the lamps will be
dimmer than before. The voltage is divided among the
different elements in the circuit.
4. TYPES OF CIRCUITS
4.1 SERIES CIRCUITS (continue)
- TOTAL RESISTANT or EQUIVALENT RESISTANT is:
Rt = R1 + R2 (+ R3, etc)
- If several generators are connected in series, the voltage will
be:
4. TYPES OF CIRCUITS
4.2 PARALLEL CIRCUITS
In parallel circuits different components are connected on
different branches of the wire. If you follow the circuit diagram
from one side of the cell to the other, you can only pass through
all the different components if you follow all the branches.
The current is shared between each component connected in
parallel. The total amount of current flowing into the junction,
or split, is equal to the total current flowing out. The current is
described as being conserved.
4. TYPES OF CIRCUITS
4.2 PARALLEL CIRCUITS (Continue)
In a parallel circuit, if a lamp breaks or a component is
disconnected from one parallel wire, the components on
different branches keep working.
And, unlike a series circuit, the
lamps stay bright if you add more
lamps in parallel. This happens
because all elements in the circuit
have the same voltage.
4. TYPES OF CIRCUITS
4.2 PARALLEL CIRCUITS (Continue)
- TOTAL RESISTANT or EQUIVALENT RESISTANT is:
4. TYPES OF CIRCUITS
VIDEO: http://www.bbc.co.uk/education/guides/zddp34j/activity
QUESTION: Which of the circuits here are connected in series,
and which are connected in parallel?
4. TYPES OF CIRCUITS
4.3 MEASURING VOLTAGE AND CURRENT
HOW TO MEASURE CURRENT:
Ammeters are used to measure
current. To measure the current
flowing through a component in a
circuit, you must connect the
ammeter in series with it.
HOW TO MEASURE VOLTAGE: Voltage is a measure
of the difference in electrical energy between two
parts of a circuit. The bigger the difference in
energy, the bigger the voltage. Voltage is measured
using a voltmeter. To measure the voltage across a
component in a circuit, you must connect the
voltmeter in parallel with it.
4. TYPES OF CIRCUITS
4.4 MIXED CIRCUITS
Some elements are connected in series and some in parallel:
RT = RP + RS; 1/Rp= 1/10 + 1/7; RP = 4,1k; RT = 5k + 4,1k = 9,1k
IT = VT/RT; IT = 9V/9,1k= 0,98 mA
V5k=IT·R5k = 0,98 mA·5k= 4,9 V ; V7k=V10k = 9V-4,9V = 4,1 V
I7k = V7k/R7k = 4,1V / 7k = 0,58 mA ; I10k= 4,1V/10k = 0,41 mA
(IT = I7k + I10k = 0,58mA+0,41mA=0,99mA)
Rs = 250+1000=1250Ω; 1/RT= 1/Rp= 1/100 + 1/1250; RT = 92,6Ω
IT = VT/RT; IT = 9V/92,6Ω = 0,097A; V100= 9V; I100=V100/R100 =
=9V/100Ω=0,09A; IT=I100+I1250; I1250=0,097A-0,09A=0,007A;
V250=0,007A·250=1,75V; V1k = 9-1,75V = 7,25V
Rs = 10k+10k=20k; 1/RT= 1/Rp= 1/20 + 1/10; RT = 6,7k
IT = VT/RT; IT = 9V/6,7k = 1,34mA; V10k= 9V; I10k=V10k/R10k =
=9V/10k=0,9mA; IT=I10k+I20k; I20k=1,34-0,9=0,44mA;
V10k-10k=0,44mA·10k=4,4V
5. TYPES OF CURRENT
5.1 DIRECT CURRENT
If the current flows in only one direction it is
called direct current, or DC. Batteries and solar
cells supply DC electricity. A typical battery may
supply 1.5 V. The diagram shows an oscilloscope
screen displaying the signal from a DC supply.
5.2 ALTERNATING CURRENT
If the current constantly changes direction it is
called alternating current, or AC. Mains electricity
is an AC supply. The Spain mains supply is about
230 V. It has a frequency of 50 Hz, which means
that it changes direction and back again 50 times
a second. The diagram shows an oscilloscope
screen displaying the signal from an AC supply.