Category: electric power distribution

What is the hum you hear when walking under large power lines?

Lou Bloomfield Leave a comment

What is the hum you hear when walking under large power lines?

The electric currents in those lines are reversing 120 times a second in the United States (60 full cycles of reversal, over and back, each second). That means that the electrostatic forces between the charges they carry and anything nearby reverse 120 time a second and the magnetic forces that they exert on one another when currents flow through them turn on and off as well. You hear all of the motions that are caused by the pulsating electric and magnetic forces.

How can we talk about positive particles flowing through wires when it is really…

Lou Bloomfield Leave a comment

How can we talk about positive particles flowing through wires when it is really negatively charged electrons?

The fiction of current being carried by positive charges really does work nicely. If a wire is carrying negatively charged electrons to the east, then the east end of the wire is becoming more and more negative and the west end is becoming more and more positive. The same would happen if that wire were carrying positively charged particles to the west. Even though these positively charged particles aren’t really there, we can pretend that they are. By pretending that current is carried by positive particles, we don’t have to worry about the arrival of a positive number of negatively charged electrons lowering the voltage of an object.

What is the purpose of the iron core in a transformer?

Lou Bloomfield Leave a comment

What is the purpose of the iron core in a transformer?

The iron core of a transformer stores energy as power is being transferred from the primary circuit to the secondary circuit. This energy is stored as the magnetization of that iron. The transformer needs to store that energy for roughly one half cycle of the alternating current or about 1/120th of a second. The more iron there is in the transformer, the more energy it can store and the more power the transformer can transfer from the primary circuit to the secondary circuit. Without any iron, the energy must be stored directly in empty space, again as a magnetization. But space isn’t as good at storing magnetic energy as iron is so the iron increases the power-handling capacity of a transformer. Without the iron, the transformer must operate at much higher frequencies of alternating current in order to transfer reasonable amounts of power.