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.
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.
When batteries are connected in parallel, the voltage remains the same, but the current that can flow in the circuit increases.
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