OMC VHS: Electricity - No Mystery!

Añadido: 2026-05-22

[00:00:32]Electricity.

[00:00:34]The ancients knew it only as a mysterious and terrifying force called lightning.

[00:00:40]Today, electricity works for us in an infinite number of ways. We use it to create to move us to see, even to help us think and remember.

[00:01:02]But to many people, electricity is still the mysterious force that the ancients feared.

[00:01:09]Electricity sometimes seems mysterious because we can't see it. We can only see its effects. And we sure don't want to feel electricity.

[00:01:20]But its behavior is very predictable. So it really isn't hard to understand how electricity works.

[00:01:28]What is electricity?

[00:01:31]It is a force of nature, a form of energy like light, heat, or gravity.

[00:01:37]Electricity is really the flow of electrons. Those tiny subatomic particles that orbit the nucleus of most atoms.

[00:01:46]Everything from the Rocky Mountains to your eyelashes contains incredible numbers of electrons.

[00:01:53]What makes electrons special and makes electricity possible is that each electron has a tiny charge, a force that draws it toward the protons locked in the atom's nucleus.

[00:02:07]The electron has what we call a negative charge, while the proton has a positive charge.

[00:02:15]The electron's negative charge tries to push it away from other electrons.

[00:02:20]This phenomenon that opposite electrical charges attract each other and like charges repel each other is one of the fundamental laws of nature.

[00:02:34]In most of nature, electrons and protons are present in equal numbers and their negative and positive charges cancel each other out.

[00:02:44]When an object has an excess of electrons like the negative terminal of a battery, we say it has a negative charge or potential.

[00:02:54]By the same token, if it has a shortage of electrons like the positive terminal of a battery, we say it has a positive charge.

[00:03:06]When a suitable path connects the two terminals, electrons are forced away from the negative terminal by their mutual repulsion. At the same time, the positive charge at the other terminal attracts electrons.

[00:03:22]This causes the electrons to flow from the negative terminal to the positive terminal. This flow of electrons is what we call electrical current.

[00:03:34]A good analogy is to think of electricity as water flowing under pressure.

[00:03:41]Standing water by itself can't do any work. But if you pressurize it by using gravity or a pump, you can make it perform work.

[00:03:51]The water analogy isn't perfect, but it will help us explain the workings of electricity and electrical components.

[00:04:02]An important concept to remember is that for our purposes, electricity can only travel in a complete circuit. In its simplest form, an electrical circuit generally includes a source such as a battery or generator and a load such as a light bulb or electric motor. The electricity needs a path to get from the source to the load, of course, but it also needs a path to get back to the source.

[00:04:32]Think of the source as a water pump and the load as a water wheel. Not only do we have to get the water from the pump to the water wheel, we have to get that water back to the pump. Otherwise, the pump will immediately run out of water and stop working.

[00:04:50]Fortunately for us, it's easy to control what path electricity will take and more importantly what paths it won't take.

[00:05:00]Electricity travels relatively easily through any metal. It travels through water if certain compounds such as salt or sugar are dissolved in that water.

[00:05:12]Substances that will carry electricity are called conductors.

[00:05:17]But conductors are the exception to the rule. For almost all other substances, including glass, plastic, and air, electricity will not flow through them in significant amounts unless the energy level is exceptionally high like lightning.

[00:05:37]These substances are called insulators.

[00:05:41]By using conductors and insulators, we can easily control electricity's path and make it do what we want.

[00:05:51]Think of wires as pipes that direct the flow of our water. Not only do they connect our water pump to our water wheel, but we can install switches in the wires. These act as valves to turn the water off and on or direct it to the circuit of our choice.

[00:06:11]We can also install other devices in the wires such as diodes which act like one-way valves. They'll let electricity flow in one direction, but they'll stop it from flowing the opposite direction.

[00:06:24]Switches and diodes are just two of the devices we can use to control the flow of electricity.

[00:06:31]Soon we'll see how to use them to make electricity do what we want.

[00:06:37]Electricity can be created by either chemical reactions or by using magnetism.

[00:06:44]A battery is an example of chemical reactions creating electricity.

[00:06:49]Sulfuric acid reacts with the lead plates in the battery creating an electrical charge across the terminals.

[00:06:58]If we use that energy, say by running a starter motor, it will chemically alter the lead plates and reduce the batteries potential.

[00:07:08]Eventually, we could run down the battery.

[00:07:11]However, if we take an electric current from another source and run it backwards through the battery, it will chemically restore the lead plates and our battery will be charged again.

[00:07:24]Magnetism will let us convert mechanical energy to electrical energy. And this is because magnetism is closely related to electricity. In fact, scientists consider them two forms of the force they call electromagnetism.

[00:07:40]If you wrap a wire into a coil and move a magnet back and forth inside that coil, the magnetic field surrounding the magnet will generate an electrical potential in the coil. This is called electromagnetic induction.

[00:07:57]Alternators use this principle to generate electricity. In our water analogy, you can think of them as water pumps. As long as you turn the pump, you can pressurize water and use it to perform work.

[00:08:14]Let's take a closer look at how an outboard alternator works. The flywheel contains magnets inside its rim.

[00:08:22]Underneath the flywheel, mounted on the power head, is a stator, a metal frame wound with wire. When the flywheel rotates, it moves magnets past the stator. This induces a magnetic field in and around the metal core of the stator.

[00:08:41]This magnetic field, constantly changing as the magnets pass the stator, produces an electrical potential in the wires wrapped around the core.

[00:08:52]But there's a twist. When the north pole of the magnet passes the stator, the electricity it generates flows in one direction. When the south pole passes the same stater pole, the electricity flows in the opposite direction. This is called alternating current or AC for short.

[00:09:14]Unfortunately, we can't use AC for our outboards electrical system.

[00:09:20]To operate the boat's electronics, charge the battery, or run accessories such as power trim and tilt, we need electricity that flows constantly in one direction only. This is called direct current or DC for short.

[00:09:40]By using a device called a rectifier, we can turn alternating current into direct current.

[00:09:47]Most outboard rectifiers use a bridge of four dodes.

[00:09:52]Remember, the diodes act like one-way valves for electricity.

[00:09:57]No matter which way electricity flows into the rectifier, the dodes will rectify it. So, it always flows out in the same direction.

[00:10:09]Electricity's close relationship to magnetism gives us more useful devices.

[00:10:15]One is called a solenoid.

[00:10:18]We already know that moving a magnet inside a coil of wire will induce a potential in that wire.

[00:10:26]This works both ways. If we run current through a wire, it will induce a magnetic field around the coil.

[00:10:35]We can use that field to magnetically attract a non-magnetized piece of iron or steel.

[00:10:43]If we attach that piece of iron to a valve, for example, we have a primer solenoid that we can use to enrich the fuel air mixture when the engine is cold.

[00:10:56]The motor takes this principle one step further.

[00:11:00]Let's take an iron core and mount two coils on it. We'll mount it on a rotating shaft and we'll call this assembly the armature.

[00:11:12]Then we'll position a pair of magnets around that shaft. These are our field magnets.

[00:11:20]Now, when we run current through the coils, they'll be attracted to one of the field magnets and repelled by the other. This attraction and repulsion turns the armature.

[00:11:35]Now we'll add a device called a commutator to the armature.

[00:11:40]Two wires called brushes contact the commutator.

[00:11:46]As the armature rotates, the commutator acts as a switch, automatically reversing the current in the coils when they pass the field magnets.

[00:11:56]Now they'll repel the magnet close to them and attract the magnet on the other side of the motor. This makes the armature spin even faster.

[00:12:06]Because our motor has two coils, it's called a two- pole motor. It has one problem. If it stops with both poles facing the field magnets, as it probably will, we can't get it started again.

[00:12:20]That's why motors almost always have an odd number of poles. A three, five, or seven pole motor will never stop at a dead spot.

[00:12:32]Motors are useful for starting our outboard engine and for operating the trim and tilt system, just to name two functions.

[00:12:41]Like our water wheel, the amount of work we can get an electrical circuit to perform depends on several factors.

[00:12:49]One factor is the pressure of the water.

[00:12:52]If we increase the pressure, we can make the water wheel turn faster and make it do more work. In electricity, this pressure is called voltage. And it's measured in units called volts.

[00:13:07]The more voltage or pressure that a source has, the more work you can get it to perform.

[00:13:14]For example, increasing the voltage will make a motor run faster or a light bulb burn brighter.

[00:13:22]Another factor is the amount of water flowing. If we install a T in our circuit and add another water wheel, it will require more water to operate the two wheels. In electricity, this amount is called amperage and it's measured in units called ampers or amps for short.

[00:13:43]We say that a given circuit draws a certain number of amps. To use our water analogy again, we can't directly control how much water flows through our water wheel. But if we take other steps such as increasing the pressure of the pump or using bigger pipes, this will allow more water to flow.

[00:14:06]Likewise, increasing the voltage or reducing the resistance of a circuit will cause the amperage to increase.

[00:14:15]If you want to measure how much power is behind our water wheel, you would measure how much water is flowing through it and the pressure of that water.

[00:14:25]Likewise, the amount of electrical power flowing through a circuit depends on both the amperage and the voltage.

[00:14:34]Electrical power is measured in watts, which equals the volts times the amps.

[00:14:41]A 12volt circuit that draws 3 amps, for example, would be rated at 36 watts of power.

[00:14:51]Of course, there's something working against all this. The water wheel slows the water flowing through it, reducing the amount of water we can push through it. The pipes connecting the pump to the water wheel restrict the water flow further.

[00:15:06]In electricity, we call this resistance and it's measured in units called ohms.

[00:15:12]All circuits have some resistance in them and we must supply enough volts and amps to overcome this resistance so the circuit can perform the work we want it to do.

[00:15:24]The voltage, amperage and resistance of a circuit are related to each other through a series of equations called Ohm's law.

[00:15:34]One expression of this is current symbolized by I equals volt divided by resistance.

[00:15:42]From this we can determine that if we double the voltage in a circuit and the resistance remains constant, the amperage will also double.

[00:15:52]If the voltage remains constant and we double the resistance, the amperage will be cut in half.

[00:15:59]There are several ways to express Ohm's law, but they all establish the same relationship between volts, amps, power, and resistance.

[00:16:11]There are two basic kinds of electrical circuits, series and parallel. In series circuits, the electrical components are connected so all of the current flows through all of the components.

[00:16:24]In parallel circuits, the components are connected side by side. So the current flow is divided among the components.

[00:16:33]How these components are connected affects the voltage and it affects the amperage going through them. Let's assume that our components have the same resistance.

[00:16:44]When you connect them in series, the amperage flowing through both is the same, but the voltage acting on each component is cut in half.

[00:16:54]For example, if we connect two motors in series and supply them with 12 volts and 6 amps, each motor will receive 6 amps, but only 6 volts.

[00:17:07]By the same token, if you added a third motor, each motor would still receive 6 amps, but only 4 volts.

[00:17:16]If we connect two motors in parallel, each motor will receive the full 12 volts but only 3 amps. Likewise, if we connect a third motor in parallel, that motor will also receive 12 volts, but each motor would only receive 2 amps.

[00:17:36]These principles also hold true for electrical sources. For example, our 12volt battery is actually six cells that generate 2 volts each. Connected in series, they give us our 12 Vs. Two cautions are in order. First, the example we've discussed assumes that all of our motors have equal resistance.

[00:18:01]If the motors had different resistance, the distribution of volts and amps would not be equal since electricity always seeks the path of least resistance.

[00:18:13]Secondly, not all circuits are easily classified as series or parallel.

[00:18:20]Many circuits contain a number of components and may have some of them connected in series and others in parallel.

[00:18:30]Electricity may seem mysterious until you learn that its behavior is predictable and relatively easy to comprehend.

[00:18:40]A good understanding of how electricity works is essential to effectively troubleshoot electrical problems and keep the customer satisfied.