Amps, volts, watts, and ohms are the four basic concepts you’ll deal with anytime you work with electricity. Together, they describe how electrical energy flows, how much resistance it encounters, and how much usable power is produced.
While these terms can feel overwhelming at first, you don’t need an engineering degree to understand how electricity works or how to use it confidently in real-world applications.
Similar to how water flows through a hose, electricity is the flow of electrons through a conductor. In most electrical systems, the conductor is a wire.
Since you can’t easily see electrons, we’ll use a water and hose analogy below. Let’s jump into it by explaining each concept on its own.
The ampere, or amp for short, is the unit of measure for electrical current. Current is the speed or rate at which the electrons flow through a conductor and is represented by the letter “I” in electrical equations.
In our water analogy, electrical current is equivalent to the flow rate or amount of water flowing through the hose.
Volts are the unit of measure for electrical voltage and are represented by the letter “V” in electrical equations. Voltage is the difference in electrical potential, or the number of electrons, between any two points in an electrical circuit.
In our water analogy, voltage is equivalent to water pressure. This pressure is the force that moves the water through the hose, just like voltage pushes electrons through a conductor.
Ohms (Ω) are the unit of measure for electrical resistance in a conductor and are represented by the letter “R” in electrical equations. Resistance tries to slow down the flow of electrons.
In our water analogy, resistance is the diameter of the hose. A wide hose has very little resistance and allows water to flow through it quickly. Conductors with low electrical resistance, like copper wire, allow electrons to flow easily through them, just like the wide hose.
Watts are the unit of measure of power and are represented by the letter “W” in electrical equations. Power is the rate at which electrical energy is transferred in a circuit. In electrical equations, the letter “P” represents power.
Power is a little harder to explain using the water analogy. With a hose, you can increase the power by either increasing the amount of water coming out or increasing the water’s pressure coming out. In an electrical system, you can increase the power by increasing the current or increasing the voltage.
It’s important to understand these basic concepts on their own, but the real fun happens when we tie amps, volts, watts, and ohms all together.
Ohm’s Law relates voltage, current, and resistance. It is represented by a simple equation.
V = I * R
V = voltage (volts)
I = current (amps)
R = resistance (ohms)
If you keep the resistance the same and increase the voltage, the current has to increase. Like in our hose analogy, if you increase the pressure, then more water will flow through it.
Resistance works against voltage to slow down the flow of electrons. If resistance increases while the voltage stays the same, the current flowing through the circuit will decrease. Similarly, if you pinch the hose to create a smaller diameter or increase the resistance, less water comes out of the end.
To bring together watts (power), amps (current), and volts (voltage), we need one more simple equation.
P = V * I
P = Power (watts)
V = voltage (volts)
I = current (amps)
Looking back at our example of water flowing through a hose, we can now see how power is directly related to current and voltage using this equation.
For example, imagine that you’re spraying the hose to turn a water wheel. The faster the wheel turns, the more power it generates.
If the hose size remains the same, we can make the wheel turn faster in two ways. The first is to increase the flow rate, which means more water and weight are hitting the wheel and spinning it faster. The second way is to increase the water pressure so that the water hits the wheel with more force and turns it faster.
In our analogy, the water flow rate is equivalent to current, and water pressure is equal to voltage. As the equation above shows, if you increase either the current or the voltage, your power will also increase.
Electrical efficiency describes how effectively electrical power is converted into useful work rather than being lost as heat. In any electrical system, some energy loss is unavoidable—but understanding amps, volts, watts, and ohms helps minimize it.
Resistance (ohms) is the primary source of inefficiency. As current flows through a conductor, resistance causes some energy to be lost as heat. Higher current increases these losses, which is why many electrical systems use higher voltage to deliver the same amount of power more efficiently.
In simple terms, electrical efficiency improves when:
This is why wire size, connection quality, and system voltage all play a critical role in electrical performance and safety.
Understanding the theory behind amps, volts, and watts is one thing — but knowing how to actually measure them brings your electrical knowledge full circle.
Fortunately, you don’t need fancy lab equipment to get accurate readings. A simple digital multimeter will do the job for most applications.
To measure voltage, set your multimeter to DC volts (V⎓). Touch the red probe to the positive terminal and the black probe to the negative terminal of your battery or circuit. The reading will show how much electrical pressure is available.
To measure current, your multimeter must be connected in series with the circuit so that all current flows through it. Set the multimeter to DC amps (A⎓), then connect it between the power source and load. This will tell you how much current your device or appliance is drawing.
Most handheld multimeters don’t directly measure watts. They measure volts and amps, and then you calculate watts by multiplying them together. Just as we learned above:
P = V x I
Watts = Volts × Amps
In practice, most people measure them “directly” using meters that do the math for them. These include:
Resistance is measured in ohms (Ω) and tells you how much a material or component resists the flow of electrical current. Measuring resistance is useful for checking wiring, testing components, and troubleshooting electrical problems.
To measure resistance, you’ll again use your trusty digital multimeter set to the ohms (Ω) setting.
Resistance must always be measured with the circuit powered off, as testing resistance on a live circuit can damage the meter or produce inaccurate readings.
Touch the multimeter probes to each side of the wire, fuse, or component being tested. Polarity does not matter when measuring resistance. The display will show the resistance value in ohms.
Resistance directly affects how much current flows for a given voltage, which is why it plays a critical role in electrical performance and troubleshooting.
The relationships between power, current, voltage, and resistance seem overwhelming at first, but they’re pretty simple once you dig in. Now that you have a basic understanding of the fundamentals of power and electricity, you should be able to tackle basic electrical projects and power systems with a little more confidence.
A: Amps, volts, watts, and ohms each describe a different aspect of electricity.
They are connected by two core relationships:
Together, these four values explain how electricity moves through a circuit, how much it is restricted, and how much usable power is produced.
A: A simple way to understand these electrical units is to compare electricity to water flowing through a hose.
Changing any one of these affects the others. More pressure, more flow, or less resistance can all increase power.
A: Electrical shock is caused by current (amps) flowing through the body.
Voltage provides the force that pushes current, and resistance limits how much current can flow. Watts describe total power, but they do not directly determine shock risk.
The severity of an electrical shock depends on several factors working together, including the amount of current, the voltage level, the resistance of the body, the path the current takes, and how long contact lasts.
A: Resistance controls how easily electricity can flow through a circuit. Higher resistance reduces current, while lower resistance allows more current to flow for the same voltage.
Resistance matters because it:
Even small increases in resistance—such as from loose or corroded connections—can reduce performance and create heat.
A: You can calculate current using the power equation:
Amps = Watts ÷ Volts
For a 1500-watt device operating at 120 volts:
1500 ÷ 120 = 12.5 amps
This is a common real-world example because many household appliances operate around 1500 watts. Resistance is already built into the appliance, which determines how much current flows at that voltage.
A: No single electrical value tells the whole story.
Understanding how all four interact helps you size circuits correctly, avoid overloads, troubleshoot problems, and work more safely with electrical systems.
We know that building or upgrading an electrical system can be overwhelming, so we’re here to help. Our Reno, Nevada-based sales and customer service team is standing by at (855) 292-2831 to take your questions!
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9 thoughts on “Amps, Volts, Watts, and Ohms: Differences Explained in Simple Terms”
Question…if my Class B runs on 30 amp, what device is needed to plug into/receive power from a normal house outlet?
Hi Suzanne, happy to help with this one! Our team suggests using just an adapter to a 110V device will be enough for your rig! Please let us know if you have any additional questions and have a great rest of your afternoon.
I want to build a camper can I the spring. I want a BattleBorn lithium battery for my electric needs. I want to power:
Keurig Mini coffee maker 1470 watts
Lasko MyHeat 200 watt space heater
NuWave PIC FLEX induction 1 burner hot plate
Uses 600, 900, or 1300 watts
12v heated car blanket
I would like to use 30 amp shore power or solar or driving the van to charge the lithium battery. Will I need an inverter, converter, or router or all 3 ? How much solar will I need ?
Hi Carol, thank you for reaching out. Our team is able to provide a thorough assessment of your system and what it will need. Please give them a call at 855-292-2831 and they will be more than happy to help!
I just wanted to say thank you for providing this. I’m a 30 year old woman and I’m ashamed to say, I don’t understand basic science. But I’m doing something about it! This is by far the best explanation I’ve found of Volts, Watts, Amps and Ohms. It’s really helped me to better understand electrical science. Thank you again!
What does the asterisk stand for in the 2 example equations ?
It’s another way to represent multiplication
I appreciate this break down on the different components of electricity. I am actually studying for a water exam where we use 460V motors and I need to have the basics down. I really liked the water comparison. It allowed me to make sense of it all.
Cheers!
Thank you for breaking down complex electrical concepts into simple, easy-to-understand language! The water analogy was especially helpful in making sense of amps, volts, and watts.