Amps vs Wattage -The Relationship Between Explained

In this article, we are going to break down the differences between Amps vs Watts as well as Volts and OHMS.

What is the difference between Amps vs Wattage?

Answer: Amps equals the measurement of flow. Volts equal the energy that is being pushed through a circuit and wattage is an expression of power.   

Simply put, Amps equals the measurement of flow. Volts equal the energy that is being pushed through a circuit and wattage is an expression of power.

What are Amps:

Amp which stands for ampere is a unit of measurement of electrical current. It represents the flow or rate at which charge moves through a conductor such as wires. Amp can be measured in various ways and one of the most common ways is by using an Ammeter.

Amps vs Wattage / Power

Watts are referred to as power while amps represent the amount of electrical current going through a wire or electricity flow.  Thus, when you have a high amp going to your device it will drain the battery faster than having a low amp on your device because electrical current is directly proportional to power (watt).  

So if you have 10 amps going into your device it will use 10 times more energy than when only 1 amp goes into your device.

What are Watts:

Wattage stands for watt. It is a unit of measurement to determine the power consumption rate of an electrical device.  It is measured in two main way: kilowatt-hour and by looking at your electricity bill which lists you total KWH used.

It is used to measure the power of appliances such as air conditioners, refrigerators, television, etc.

If you have an electrical device that uses 100 watts, it means the item consumes or uses 100 watts every hour.  When electricity is at 12 volts and running at 10 amps then this would be 1200 watt hours per hour which equates to 1.2 KWH or if you measured in kilowatt-hour this would be equal to 1.2 kW hours per hour (if using a 1000 watt device).

This also relates to amps because higher amperage = larger amounts of energy being drained from the battery meaning less time your device runs depending on the amp rate vs voltage (volts).  

A good example is when you are running your car stereo which uses a lot of amps, if you have the amp at 10 amps and the voltage low be it 12 volts and 1 amp or 14.4 volts and 2 amps:  you will drain your battery faster than having higher voltage with lower amperage because its equates to more energy being drained from your car's battery.

How many watts are in an amp?

  • 1 amp = 1 watt
  • 1 amp x 1200 watts = 1.2 KWH

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What are Volts:

Volts is simply electricity pressure measured in volts (V).  It is used to measure the amount of power that goes into a device whether it's AC or DC appliances.

Volts is simply electricity pressure measured in volts (V).  It is used to measure the amount of power that goes into a device whether it's AC or DC appliances.

Voltage is a measure of difference in potential energy between two points on a conductor, which is usually expressed as the difference in electric potential (volts), but may also be expressed as the electromagnetic force (volt) across the contacts of a relay.

For example, if you had 12 volts going into your device then that means if you were to touch both positive and negative sides of your battery at once you would get shocked because power has been transformed from one form to another resulting electricity (which carries electrons).

These electrons are what flow through wires or cables when connected to an electrical circuit. Voltage can be mathematically described by Ohm's Law (see below for Ohm's Law)

Volts vs Amps Vs Ohms (Resistance)

The relationship between voltage, amps and resistance are very similar but ohms is different since it does not have any electrical current flow, while voltage and amps both do have current flow.

When you increase the volts on your circuit it means there will be more electric pressure which cause current to go through a wire or device thus draining battery faster if high amps are going to that wire or device. The higher the volts put into DC circuit the higher the amps will be going into that circuit.

When you increase the ampere on your device it means there will be more electric flow which cause electricity to go through a wire or device thus draining battery faster if high wattage is going to that wire or device. So when you have high amp going to your device it will drain the battery faster than low amp.

- You may like: What Are AC and DC Power Systems?

Volts vs Ohms

Voltage is a measurement of pressure between two points in an electric field, while ohm refers to resistance of an object for a current flow.   A resistor limits current by providing resistance and converts voltage into heat (energy) instead of allowing electrons to pass straight through as they do with conductors like wire. It is measured in Ohms (Ω).

Volts, voltage and electricity pressure are similar because they all have current flowing from a power source then that completes a circuit to an electrical device.  It is measured in volts (V) which means its unit of measurement is volt.  You measure this when your battery discharges the amount of watts it provides to devices.  

A watt is the unit of power that is equivalent to one joule per second, which makes a watt equal to 3.4x10^3 (power) thus making any device when on 1 amp will be using watts or if you use 12 volts battery with 100 amps your using 1200 watts.

Amps and electric flow is similar because they both carry current to your device.   They are measured in amps (A) which means its unit of measurement is amps.  You measure this when your battery discharges the amount of energy it provides to devices.  This is called watts or how much power a device draws from the battery. 

Voltage vs Resistance and Power

Voltage is the amount of pressure (or force) which pushes electrons through a wire to power your devices such as TVs, cellphones, laptops, lamps etc.  It is also referred to as potential difference or electromotive force (EMF).

Voltage is measured in volts which represents potential energy per charge i.e unit of work done per unit of charge when moving between two points of different voltage levels.

The same way ohms represent resistance that hinders or slows down the flow of current like water in a pipe with more holes than bigger ones will have less flow then a pipe with big enough hole for water to go through freely without hinderance (lesser resistance).

The relationship between voltage, resistance and power is:

P=IE or Power (watts) = Current (amps) x Voltage (volts). Thus if your device had 10 amps going into it with 5 volts your calculating P which equals 50 watts  which equals 10x5. Now you know how to calculate watts from ampere and volt.

Power represents amount of work done per unit of time so a more powerful device like laptop uses more power because the CPU in that case has higher frequency thus process data faster as well as plays video games or watch videos at high resolution.

Same way, an electrical circuit also called load when connected to source such as 110VAC will need different amounts of power depending on what is connected to it.  

The same way power can be converted into heat for instance if you put a 10 amp load on a 12v battery that flows through wires and the electrically heated wire produces heat which causes the water inside your heater / boiler to boil thus producing steam or hot water.

What are OHMS?

Resistance describes the degree to which a material opposes, or resists the flow of electricity through it.  The electrical resistance is measured in ohms (Ω) where lower number means greater resistance and higher number shows less resistance to current flow.

Amps vs Volts then relate to Ohms:

Ohm is a unit of measurement for electrical resistance. Electrical current flows through all conductors including wires


Ohm's law also called Ohm's voltage-current relation states that the voltage across a conductor between two points is directly proportional to the applied potential difference; while voltage, electrical current and resistance are indirectly proportionate given that there is no change in temperature among other conditions .

When one increases /decreases so does the others do with it but not necessarily by same ratio if at all.

  • Current = Voltage ÷ Resistance: If you want 5 amps to flow through a 2 ohm resistor, then you will have to apply 10 volts: 5 ÷ 2 = 1.5 amp x 10 V = 15 watts of power .
  • Voltage = Current × Resistance or V=IR: If the resistance is increased, the voltage dropped and vice versa.   For example if the current was doubled but at same resistance, the voltage drop is half of its original value. If we use Ohms law (V= IR) it becomes more clear how this works: V/I= R  so doubling I would mean halving R and therefore inversely proportional which means it's opposite each other thus lowering one causes increase in another .
  • Power = Current x Voltage or P=I x E or P=VI: Since P = VI, then V=P/I and I = P/VI. So if you want to power an electrical circuit with a certain amount of current at a given voltage, first calculate the load in watts and then multiply that number by volts . For example if you want to have 6 amps flow through your circuit at 12 volts, you would need 75 watts of power: (6A)x(12V).

If voltage is doubled while electrical current remains unchanged we double the power (power=voltage^2 / resistance).  Imagine a wire with length 100 meters which has 1 amp flowing through it due to 20 volt battery.

This means it's loosing 10 Joules per second.  If we had 2 amps flowing through it, then it would lose twice that rate (20 Joule/s).

Further if we get 4 amp to go through the wire, then the loss of energy will be four times more than what it was when there was only 1 amp going through.

You could say power is like money; current – voltage = resistance is like a pipe with water being applied pressure and flow outwards. The amount of water that flows through the pipe depends on how much time you apply pressure, which in our case is voltage at given resistance .

If your having big hole in your pipe so as soon as you start applying pressure you already have some water flowing down but if you have small hole plugged up by some putty then it will make a bit harder to get water down the pipe and thus more pressure is needed.

If you are having bigger hole in your pipe, there will be more water flowing through it but not necessarily by the same ratio, meaning if you apply 10 volt across 2 ohm resistor (P=VI), then in reality larger amount of power is being wasted as some energy is lost due to heat or friction thus making current less than what you would think .

It's something like driving car with huge engine that can run at high RPM although when running at certain rpm we are loosing some energy off-put from the actual physical means of fuel which is combusting under our piston heads.  In short, for best results and to get most power out of the source, we have to use lower voltage and higher current.  

If you want even more heat flowing through that resistor, just turn up your voltage since heating is related to rate at which energy is being lost . If you wanted less heating in resistor then you could turn up resistance. This means if there was an infinite amount of current then there would be zero amount of watts loss due to it having zero ohms.

The same goes for resistance (infinite) when applied with zero volts: no watts loss because there isn't any potential difference between two points, thus nothing happens or moves. You may think that a light bulb has high resistance but also very low amps flow through it so how do they make it glow?

By passing thousands of amps through a filament via high voltage which is why it gets ridiculously hot and turns white from black.

If you connect any source to load with the same resistance, then current must be the same for both .

If we have an electrical circuit for example with 2 lamps powered by 220 volts supply (I=V/R), if the first lamp draws 8 amps than second one must be drawing exactly 8 amp regardless of actual voltage applied to each or even number that are connected since they all share same resistance. In this case power would double for every extra lamp but also halve when only one lamp is on.

This may sound as simple concept in theory however these laws do not work effectively unless there's resistance involved.

What is the relationship between Amps, Volts, and Watts?

What is the relationship between Amps, Volts, and Watts?

The difference between amps, volts, and watts is; I (ampere) is the most familiar with from physics class.  Voltage = potential difference between two points, V=IR (potential energy per unit charge). W refers to watts which is a combination of voltage and current. Ohm's law states that Voltage = Current x Resistance, which is how we calculate the number of watts given a voltage and current.

An electrical circuit is composed of resistors, which are elements that oppose the flow of electricity. In fact, they restrict it in certain ways depending on their value (resistance).

The formula for power is equal to Voltage x Current tells us that power = V X I : if we increase either V or I , we increase the power.

Here is a great calculator if you are looking to figure it out, rather easily. 

Although resistors oppose flow of electricity, they are not perfect at doing this: some energy is lost as heat and light. The more resistance you add, the more energy is transformed into heat. This also means that if we were to figure out how much power will be wasted in a resistor of a set value, we can get the power of a non-resistant circuit that uses this resistor.

Hi & Welcome!

My name is Jeremy and I have been an avid car nut for many year. My first car was an 1987 Honda CRX. I put in my first Kenwood stereo, amp, 2 10" JLs and a CB Radio in it and have been an avid user of CBs and car radios for years. I'll do my best to share my tips, information and thoughts to help you with whatever question you might have, ABOUT ME 

After I graduated from High School, I worked 5 years are Radio Shack and 3 years at Circuit City answering questions and helping customers with various electronics questions.