Voltage

One of the more difficult things as a beginner to the world of electronics  is coming to terms with Voltage and Current. In the following tutorials we'll try to explain, with the help of simple visual aids what Voltage and Current are.

Let's look at Voltage first:

The Electrical symbol for voltage is the capital letter V.

So for example 5V means "5 Volts".

A Voltage can be:

  • Positive, denoted by the plus symbol (+).
    example: +5V, "Positive 5 Volts".
  • Negative, denoted by the minus symbol (-).
    example: -12V, "Minus 12 Volts".
  • At a steady level, referred to as direct current denoted by the abbreviation (dc).
    Example: +5Vdc, "Plus 5 Volts direct current".
  • Constantly changing between Positive and Negative, referred to as alternating current (ac)
    Example: 240Vac, "240 Volts alternating current".

For now we're going to concentrate on direct current, dc.

Most people are familiar with the common domestic battery like the AA's and AAA's, but how can we better understand what voltage is. A typical AA battery has a voltage of 1.5V. To try and make this easier let's compare this voltage to a tank full of water. The Voltage is the pressure of the water pressing down onto the bottom of the tank.

 


SINGLE CELL

 
=

1.5V

  =  1.5Vdc
Tank x 1 Cell x 1
The length of the arrows show the pressure on the bottom of the tank, the number of arrows show that this pressure is evenly distributed. Now think of the length of the arrows as Voltage. The length of the arrows is equivalent to 1.5V evenly distributed across the battery.


PARALLEL

 
=

1.5V

1.5V

  =  1.5Vdc
Tank x 2 Cell x 2
in Parallel		 Cells in Parallel 
Voltage stay the same.

If we now put two water tanks side by side, although the volume of water has doubled the length of the arrows show that the pressure is still evenly distributed across the tank and is the same as the single tank in the previous example. Thus the Voltage remains the same (1.5V) but the capacity  has doubled. This new composite cell will last twice as long. 


SERIES

 
= 1.5V  =  3Vdc
1.5V
Tank x 2 Cell x 2
in Series		 Cells in Series
Voltages added together.

However if we now put the two cells one on top of the other the capacity has still doubled but look what has happened to the length of the lines (Pressure), they have doubled in length. This means that there is now twice the Voltage (2 x 1.5 = 3V). Although the capacity has doubled pressure has also doubled and this new composite cell will discharge in the same time as the single cell.

Let's recap on what we've learned so far:

In the next tutorial well have a look at Current.

 

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