Basic HTML Version
2
Series and parallel circuits
W
hen the components in a circuit are linked up
1
one to another, end to end, they form a
series
circuit
.
Resistors R
1
and R
2
are in series both with each other
and with the battery. The result is that there is only
one path for the electrons flow along. Thus the current
is the same in each of the components of the series
because the free electrons, moving away from one
point, are continuously replaced by free electrons
flowing from an adjacent point in the series circuit.
All electrons move at same speed as those leaving the
battery. Thus, electron
drift
is the same throughout
2
the circuit, with an equal number of electrons moving
at the same time at the same speed. Which is why
the current is the same in all parts of a series circuit.
Furthermore, the total resistance Rt of a series string
is equal to the sum of the individual resistances.
However, when two or more components are
connected across one voltage source, they form a
parallel circuit
. Each parallel path is then a branch,
with its own individual current.
Thus, parallel circuits have one common voltage
across all the branches, but individual branch currents,
may be different.
Parallel circuits are usually used to
wire a house
up
to the power lines. Houses have many lights and
appliances connected across the 120 V source.
The
wall receptacle
has a potential difference of
120 V across each pair of terminals.
Therefore, each operates independently of any other
appliance
with all the individual branch circuits
connected across the 120 V line.
Lastly, there are circuits called
series-parallel
circuits
, because some components are connected in
series in order to have same current, while others are
in parallel so as to have the same voltage. This type
of circuit is used where different amounts of current
and voltage with one source of applied voltage have
to be provided.
1
linked up
: connected
2
throughout (the circuit)
: in every part of/everywhere in (the
circuit)
In Series or in Parallel
10
Brainstorming
Look carefully at the pictures below and describe them. Then read the text and
underline the main ideas.
TEXT 4
appliance
apparecchio
drift
flusso
wall receptacle
presa a muro
(to) wire a house up
eseguire il collegamento elettrico in una casa
TECHNICAL ENGLISH
A series circuit.
AMP
MP
Progetto FOR ELECTRONICS_unit_1.indd 21
10/01/