Batteries in series and parallel
Battery terminals Connecting batteries in series
Voltage and current produced by batteries in series Batteries in parallel
What is the purpose of batteries in parallel? A summary of batteries in series
A summary of batteries in 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
Click for larger image 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.
Click for larger image

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
Click for larger image 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.

Click for larger image 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.

Click for larger imageRemember 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.

Copyright owned by the State of Victoria (Department of Education and Early Childhood Development). Used with Permission.

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