An Introduction to Electricity: Volts, Amps, Resistance, and Watts

Even with all the technical information we have access to on YouTube or manuals, it’s important to understand the basics of electricity. When you know the fundamentals of how electric-powered tools function, you can confidently troubleshoot almost any problem.

The purpose of this article is to give you a better understanding of voltage, amperage, resistance, and wattage. By reading this, you will be better equipped to troubleshoot common issues with your electric chain hoist and other electric-powered equipment. 

What is Electricity and Where Does it Come From? 

In its simplest terms, electricity is the potential difference of charge (electrons) in a media, which flows from positive to negative in conventional understanding. The other thing to note is that electrons are always seeking to balance the charge. No matter how the charge is created, be it chemically in batteries or physically by friction from socks on a carpet, the movement of the electrons is electricity.

The flow of electrical charge is referred to as electric current and there are two types of current:

• Direct current (DC) – flows in one direction with a constant voltage polarity 
• Alternating current (AC) – changes direction and voltage polarity

Direct current was utilized by Thomas Edison in his pioneering development of the light bulb and he drew upon Luigi Galvani and Alessandro Volta’s research in the creation of the battery. Edison’s first major use of direct current (DC) was his lighting of a park in New York (Battery Park) with his light bulbs, a brilliant event to behold indeed. But what was noticed was that the bulbs closest to the batteries were brightest and grew dimmer the farther down the wire went. This was caused by the resistance of the wire to the electrons trying to flow through it. Due to this resistance it became clear that DC is inefficient for long-distance power transmission.

 Cue Nikola Tesla and the invention of alternating current. Through his research he invented numerous electrical devices such as motors (generators) and turbines as well as transformers that produced the higher voltages needed for long distance transmission of electrical power. There is even great debate that he may have even beaten Marconi to the invention of radio broadcasting. The genius of Nikola Tesla and his innovations power the modern world and we should never forget him.

Today, most of our personal/portable devices use DC power provided by batteries while power plants produce the AC that powers everything from the plug in the wall at home to industrial factories around the globe.

Understanding Electricity

To really get to grips with electricity, we must have a basic understanding of four electrical terms:

volts, amps, resistance, and wattage.

Volts

Voltage is a measurement of the electrical potential (or pressure) in a circuit. It is measured in volts (V) named after the Italian physicist Alessandro Volta. 

In an average US household, power from the electrical grid is delivered in 120 volts for small appliances like cell phone chargers and lamps, and 240 volts for large appliances such as washing machines and air conditioners.

Amps

Amperage is a measure of the amount of current running through a circuit. This is the rate that current—made up of electrons—is flowing through the wire. It is measured in amps (A) or amperes, named after the French physicist André-Marie Ampère.

Resistance

Electricity flows through wires but they are not perfect conductors. It means that the flow of electricity is slowed down as it moves and even more when it passes through electrical devices and appliances. Resistance is measured in Ohms (Ω) named after the German physicist and mathematician Georg Simon Ohm.

Wattage

This is a term we are more familiar with and it indicates the amount of power an electrical device consumes. Whether it be a coffee maker at around 1500 watts or a light bulb at between 40 and 75 watts, it is the electricity required to do something.

Wattage is calculated by multiplying voltage by the amperage, or V x A = W, and is named after Scottish engineer James Watt.

The Water Faucet Example

To help illustrate how volts, amps, and resistance function, we’re going to use a water faucet on the side of your home as an example. 

If you take a pressure gauge, screw it onto a faucet at your home, and then turn on the water, the pressure gauge will indicate how much water pressure you have at that faucet. It will typically read between 25 to 40 PSI for a city-supplied household.

In this example, no water is flowing. What we did was measure a static—or “potential”—water pressure. 

Now, consider an electrical outlet in your home. When nothing is plugged into the outlet, there is no electrical current flowing. That said, we can still measure the static supply voltage. This is done using a standard voltmeter and inserting the test probe leads into the outlet socket. For a conventional household, you should expect a reading of 117 to 126 volts. 

Remembering the water faucet example, you can equate water pressure to electrical voltage.

Water pressure drives the flow of water through a hose, just like voltage drives electrical current flowing in a conductor – cable or wire. 

You should also note that the word “voltage” is the same as the word “potential” when talking about electricity. They are often used interchangeably.

The key ingredient to the flow of electricity, or water, is based on the principle that opposites attract. This is what we mean by a potential difference. 

When the faucet has a gauge attached and no outlet, no water can flow because there is no potential difference. But, if we remove the gauge, attach a hose, and apply pressure (potential) by opening the faucet, water will flow. 

That’s because the water in the faucet is at a higher pressure (potential) than the open end of the hose which is at a lower—normal atmospheric—pressure (potential). 

The same is true of electricity. The electrons are always seeking balance, so they will flow from higher to lower potential. The greater the potential difference the faster the flow.

Flow Rate

Using the example again of water flowing through the hose, you could measure the flow rate by placing a one-gallon bucket at the end of the hose and time how long it takes to fill. Let’s say it takes 30 seconds. This would equate to a water flow rate of two gallons per minute.

In electrical circuits, the amount of electricity flowing through a conductor is measured in amps. 

When you think of electrical current flow, think of water flowing through a hose (gallons per minute), which is measured in amps.

Electrical Resistance

If we install a pressure gauge at the water faucet, with the hose attached and water flowing at two gallons per minute, we will likely get a reading of around 25 PSI. Another pressure gauge is then attached halfway down the length of the hose, but the reading is only 15 PSI with no clear impediment to the flowing water. 

This signifies a pressure drop of 10 PSI over the distance between the two pressure gauges. But, why does the pressure drop occur? 

It is because of frictional losses caused by the water flowing through something (the hose) that creates resistance by friction. The higher the flow rate, the higher the pressure drop will be.

In electrical circuits, resistance to current flow is the same as pressure drop in the water hose example. In the case of electricity, this resistance is measured in ohms. 

Most electrical conductors—in other words, a product such as a plug or light bulb—are rated for a certain voltage or amperage. This rating describes in non-technical terms the maximum capacity of the conductor. If you do not exceed either value, the conductor will not be damaged by the current flowing through it.

If the voltage and/or current are exceeded, the resistance developed by the elevated values will result in great resistance. This excess energy is released as heat and the conductor will continue to get hotter until it melts.

Basic Circuit Theory

Electric circuit theory is one of the most vital aspects of electrical engineering. Understanding how components work individually and collectively is the basis for designing, manufacturing, and troubleshooting all kinds of electronic devices and systems.

In the simplest terms, an electric circuit is a pathway for an electric current to flow from one point to another. 

From a high level, every circuit has three basic components:

• Voltage source: A voltage source introduces energy into a circuit via a potential difference between its positive (+) and negative (-) terminals. Voltage sources can be AC (power from the grid or generators) or DC (batteries or mains outlet).

• Conductive path: A conductive path (aka a conductor) provides a medium for current flow through a circuit. These components have a very low resistance to current, e.g. copper wires, lead solder, or metallic traces on a printed circuit board (PCB). Conductors also help link other components together to achieve a single function.
  
• A Load: A load is any device that consumes power in a circuit, such as a light-emitting diode (LED), a motor, or a relay. In the event of a short circuit, the conductor dissipates eclectic power by generating heat which can result in a fire

In the example above we are turning on a lamp by closing a switch and completing a pathway for electricity to flow through a load and do some work. 

Applying This Theory to a Hoist

To examine how the circuit can apply to a hoist, we are going to change the lamp to a device called a relay. 

This device is very helpful as it provides the ability to remotely switch a load on and off with an electrical signal rather than a mechanical lever or button. It also provides a method to isolate and control a much more powerful load with a low-voltage signal. 

The relay pictured here is a double pole, double throw (DPDT) type. The magic in this device is a simple electromagnet which is the white cylindrical shape with red lettering that says 220VAC. 

Sitting on top of the electromagnet is the pole plate. To the left, you will notice two springs going vertically. These hold the pivot end of the pole plate to the fulcrum and hold it up when the electromagnet isn’t energized.

Now, take a look at the gold-colored horizontal flat bars. There is a small white wire attached to the left that attaches to a through pin on the black base. This is called the common pole.

If you look at the right end of the pole you’ll see two more through pins and these are equipped with highly polished discs arranged above and below the pole. These are the normally closed (above) and normally open (below) contacts.

This schematic better illustrates the double-pole double-throw of the relay with the electromagnet symbolized by the coil shape on the left. The poles are configured as:

• A1, B1, and C1 are one pole with two throws
• A2, B2, and C2 are the second pole with two throws
• A1 and A2 are the normally open contacts
• B1 and B2 are the normally close contacts
• C1 and C2 are the common poles

As was mentioned earlier we are going to change things up by replacing the lamp in our circuit above with this relay. 

We are going to land a wire on each side of the holding coil (electromagnet) and replace the switch in the example circuit with a button on a hoist pendant.

When we press it downward, we complete the circuit pathway sending electrons from the battery through the electromagnet (the load) and back into the battery. The current creates a magnetic field in the electromagnet that pulls the pole plate downward. This moves the common pole from the normally closed contacts to the normally open ones, creating a pathway for current to flow from another circuit.

What’s Next?

In the spirit of simplicity, this is all we are going to cover in this article. Consider it your first lesson! Keep an eye out for articles coming very soon that delve deeper into the technical functionalities of hoist systems. We will be exploring a variety of topics such as explaining hoist power and voltage and how hoist control transformers work. 

Until then, if you have any questions regarding specific products or need some guidance on power supply requirements, contact our expert team today.