Batteries in series and parallel
It is possible to vary total voltage and current
from a number of batteries by connecting them in different ways
in the circuit. It does not matter where in the circuit the batteries
are placed, it is how they are placed with respect to each other
that is important.
Basically, they can be connected in series or in
parallel. The resultant voltage and current can be calculated by
using a few simple rules.
Battery terminals
In this picture of a battery, the protruding
bit on top is the positive terminal, and the flat bit on the base
is the negative terminal. Electrons flow from the negative terminal
to the positive terminal as they move through an electrical circuit.
A standard single dry cell battery produces
a voltage of 1.5 Volt, with its current dependent on the size of
the cell. The bigger the cell, the bigger the current.
Note:- 9 Volt batteries used in larger flash
lights are really a series of 6 cells or batteries in a single case.
Connecting batteries in series
The word series means "following on from
the previous one", like a TV series for example.
It's important to connect the batteries with their
terminals in the correct order. Batteries in series need to be connected
with the positive end of one battery to the negative end of the
next battery.
If they are incorrectly connected, the batteries
will cancel out each other's energy and quickly flatten each other.
Batteries correctly placed in series, positive to
negative, will add their output voltages, producing a greater voltage.
Voltage and current produced
by batteries in series
If two 1.5 volt batteries are connected head
to tail, the total voltage is 3.0 volt. This is because batteries
in series produce a voltage equal to the number of batteries multiplied
by the voltage of each individual battery.
Batteries with voltages greater than 1.5 volts
are made up of cells connected in series inside a single case. In
the 9 volt battery above, there are six cells connected in series.
The calculation is 6 × 1.5 Volt = 9 Volt.
When batteries are connected in series the flow of
electrons, as measured by the current, is the same anywhere in the
circuit.
A 9 Volt battery will produce a voltage 6 times larger
than a single 1.5 Volt battery in the same circuit, but the current
in each circuit will be the same no matter where the current is
measured.
This happens because the batteries are arranged
in a line, and like water flowing through different hoses connected
in a line, what goes in one end must come out the other. The same
electrons must flow through all the batteries at the same rate,
so the current must be the same in each battery and in each part
of the circuit.
Batteries in parallel
The word parallel means "alongside each
other". When batteries are placed in parallel all the positive
terminals are joined together with a single wire to one part of
the circuit, and all the negative terminals are joined with a single
wire to the rest of the circuit.
Remember
the voltage increases when batteries are in series, but with batteries
in parallel this is not the case. When two or more batteries are
placed in parallel, the voltage in the circuit is the same as each
individual battery. That is two, three, four or more 1.5 volt batteries
in parallel will produce a voltage of 1.5 Volts!
In a parallel circuit, individual electrons can only
pass through one of the alternative paths and batteries at a time,
thus each electron can only gain energy from one of the batteries
in the circuit. As voltage is a measure of the energy carried by
the electrons in the circuit, the increase in voltage for each electron
in the circuit is the same as if they had passed through only one
battery.
What is the purpose of batteries
in parallel?
When batteries are connected in parallel, the
current flowing through the circuit increases with the number of
batteries in the circuit. Each battery can pump a set number of
electrons per second, for a given circuit, so if two or more batteries
are connected in parallel the number of electrons they push out
each second and energy supplied is added, hence the total current
in the circuit is increased.
A summary of batteries in series
When batteries are connected in series, the
voltage increases.
A summary of batteries in parallel
When batteries are connected in parallel, the
voltage remains the same, but the current that can flow in the circuit
increases.