THE ELECTRIC POWER LINE (Practice)

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Welcome to the home’s electrical systems course organized by NPR Online Technologies.

Before starting the lesson we recommend that you subscribe to our youtube channel.

As indicated in the title of the lesson, this is a practical part of our course.

In these practical sessions, we will put into practice the concepts learned in the theoretical part of the course.

In particular, we will illustrate the installation techniques used in real home’s electrical systems. We will use real components, and when possible we will use low-voltage batteries to give all of you the opportunity to work with the electric circuits and at the same time avoiding electrical shock hazards.

In this lesson, we will address the power line from a practical point of view.

In the theoretical section we have seen that electricity arrives in our homes with two wires (neutral and hot) connected to the electricity meter.

We have also seen that in several geographic areas, the voltage available at the terminals of the electricity meter is equal to 230 V which is a high value and is capable of causing an electric shock in case of accidental contact with our body.

For these reasons, whenever possible, in our exercises we will replace the power line with a simple battery.

We know that the batteries differ mainly according to their shape, size, and voltage. We have for example 1.5 V, 3 V, 4.5 V, 9 V and 12 V batteries.

In particular, we will use 9 V batteries. The main reason regarding this choice, is that for these batteries, there are commercially available connectors that once connected to the battery they can provide the 9 V voltage of the battery through two wires, a red wire for the positive pole, and a black wire for the negative pole.

Starting from this choice, let’s now analyze the differences between the real power line and the one we are simulating.

First of all, the battery voltage is 9 V and is therefore much lower than that of electrical systems which for example is equal to 230 V for European countries.

As already mentioned, the use of a low voltage battery was deliberately introduced to avoid any risk during the practical sessions. We can safely touch one or both contacts of the battery without incurring electric shock.

This same operation would instead be very risky if performed on the electrical cables of our 230 V system.

A second difference is related to the fact that the battery works with a direct current and, for this reason, it has a positive, and a negative pole.

The electrical system of residential homes, on the other hand, works with an alternating current and, in this case, the available voltage changes polarity several times per second.

For this reason, in place of the negative and positive wires, we have the hot and neutral wires.

Anyway, during the practical sessions, we will point out from time to time what differences exist in simulating the power line with a 9 V battery.

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For now, we assume that there are no real differences between direct current and alternating current. Furthermore we will simulate the hot wire with the positive wire of the battery, and the neutral wire with the negative wire of the battery.

To better remember this correspondence, we will connect two wires, one brown and one blue, to the two terminals of the battery.

To do this, we must initially prepare the worktable.

It must have a minimum size of about 60 cm x 60 cm,  and must be made of wood or plastic.

Worktables made of metal or in general conductive material should not be used.

In our case, we have a wooden table on which, for our convenience, we have delimited the work area (about 60 cm x 60 cm) using colored insulating tape.

Let’s now proceed with the operation of connecting the brown and blue cables to the positive and negative poles of the 9 V battery.

For the purposes of this course, we need approximately 5 m of brown wire and approximately 5 m of blue wire.

The cross-sectional area of the conductors is not important for our exercises and we can therefore use conductors with a cross section of 1.5 mm².

To make the connection to the battery terminals, we cut two pieces of wire, one brown and one blue, approximately 40 cm long.

The two wires must be stripped on both ends. This operation consists in removing about 1.5 / 2 cm of insulation from the cable to expose the bare conductor.

This operation can be carried out with normal pliers, as shown in the figure,

or using a suitable tool called wire stripper. There are different types of wire stripper, one of them is shown in the figure.

At this point, we can connect the brown cable to the positive pole of the battery and the blue cable to the negative pole of the battery. The connection can be made by twisting the conductors together

or by using screw terminals that allow us to connect the cables by the tightening of the screws.

In the figure, the red and black cables have already been connected to the connectors,

while the blue and brown cables are about to be inserted into the screw terminals,

 as best highlighted in this zoom.

Well, we have come to the end of this lesson. We have seen how to simulate an electric power line by using a low voltage battery and we have prepared our work table for the practical sessions.

We suggest you immediately consolidate the concepts you have just learned by carefully reviewing this lessons and above all by going through all our other lessons on the subject, by accessing our playlists.

We remind you that our website is active with numerous insights on these issues.

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Thanks for your attention and … see you next time!

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