Feeling shocked about all there is to know about current density? Well, it's about time we spark off a conversation.
Whether you're an expert in the field, or a complete newbie, we going to break it down for you. When conversions get tough, use this helpful calculator to go from A/cm2 to A/m2 and more.
Keep reading below for a comprehensive Q & A guide to all of your current density queries.
When dealing with current density, the units of your variables can differ from what is typically given in the current density equation.
The easiest method to translate measurements is to use a good current density calculator.
Here you simply select the units you have and input your figure. Then select the units you need to convert them to and voila, you have the new number.
It doesn't get much simpler than that for finding new current density units.
As the name suggests, current density is literally the measure of an electric current's density.
You'll see it denoted as the vector symbol 'J'.
In technical terms (in the field of electromagnetism) it's the measurement of an electric current (in amperes) per cross-sectional unit area (in meters squared / m2).
Imagine a cylindrical metal rod laid out in front of you. The rod has an electric current traveling through it (which, as you may already know, can only travel in one direction).
Now imagine somehow slicing that rod in half.
The circular area you've created is what's known as the cross-section. Calculating the current density tells you the amount of current that's flowing across a given part of it.
And, importantly, this is a vector quantity. Meaning it has both a magnitude and a direction.
Current density is important in different domains.
Current density plays a crucial role in the design and production of electronic systems.
Electric circuit performance is dependent on the level of current it's designed for; the dimensions of the capacitors control the current density.
The demand for ever smaller circuits (to fit ever smaller devices) has led to a practice of using higher current densities to create larger numbers in the smaller chips.
But it's important to ensure current density never gets too large.
If it does, it can cause negative effects in the circuit such as melting and burning, or altering electrical properties.
But there's more to current density than electrical circuits.
It's also used to analyze the physics that underlie the very nature of solids themselves. And it's a key component in areas of physics such as Ampere's circuital law.
To measure current density you first need to know two basic things.
Once you have your two figures, simply input them into the formula (provided below) and calculate accordingly.
The standard unit for current density is amperes per m2 (amps/m2).
To calculate current density you divide current by the area. In this way, the formula for current density (J) is:
The units for current (denoted as 'I') and area (denoted as 'A') are amperes and metres squared, respectively.
This formula shows the magnitude of the current density, which is a vector quantity. As a vector quantity, it has both a magnitude and a direction.
But remember, you can't divide a quantity by a vector. However, that's a topic for another time!
Now we know how to measure current density and what the formula is, let's try to solve an actual current density problem. It's not as hard as it sounds.
Recall the metal rod mentioned above.
Let's say this is a copper wire with a current of 0.01 amperes (that's 10 thousandths of an amp) running through it. The cross-sectional area of the wire is 5mm2.
What's the current density? First, we need to convert our mm2, to the units we need: m2.
Area = 0.005 m2 (5mm / 1000)
Now, the formula we'd use to calculate the current density is as follows:
J = I / A
= 0.01 / 0.005
= 2 amps/m2
Current density can be a tricky thing to wrap your head around. But hopefully, this guide has helped clear up some of your questions about it.
Remembering that current density is literally the measure of an electric current's density is a good start.
If you can recall that it's the amount of current flowing across a cross-sectional area on a conductor, then even better.
Thankfully the formula for calculating it is fairly easy to remember too, where J = I/A.
And if you ever need to find an answer with some derivative of the typical units (amps and m2), a current density calculator is by far the easiest way to convert them!
We'd love to hear from you. Has this guide helped answer your questions about current density? Or have we left something out?
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