Hey there guys. Paul here from TheEngineeringMindset. com.
In this video, we're going to be looking at inductors to learn how they work, where we use them, and why they're important. Remember, electricity is dangerous and can be fatal. You should be qualified and competent to carry out any electrical work.
So, what is an inductor? An inductor is a component in an electrical circuit which stores energy in its magnetic field. It can release this energy almost instantly, and we'll see how it does that later on in this video.
Being able to store and quickly release energy is a very important feature, and that's why we're going to use these in all sorts of circuits. Now, in our previous video, we looked at how capacitors work. Do check that out if you haven't already, link's down below.
So, how does an inductor work? I want you to first think about water flowing through some pipes. There is a pump which pushes this water, and the pump is equivalent to our battery in the circuit.
The pipe will split into two branches, and the pipes are equivalent to our wires. One branch has a pipe with a reducer in it, and that reduction makes it a little harder for water to flow through it. So, the reducer is equivalent to resistance in our electrical circuit.
The other branch has a water wheel built into it. The water wheel can rotate, and the water flowing through it will cause it to rotate. The wheel is very heavy, though, so it takes some time to get it up to speed, and the water has to keep pushing against this to get it to move.
This water wheel is going to be equivalent to our inductor. When we first start the pump, the water is going to flow and it wants to get back to the pump, as this is a closed loop. This is just like when electrons leave the battery, they flow and try and get back to the other side of the battery.
By the way, in these animations, I use electron flow, which is from negative to positive, but you might be used to seeing conventional flow, which is from positive to negative. Just be aware of the two and which one we're using. So, as the water flows, it reaches the branches and it has to now decide which path to take.
The water pushes against the wheel, but the wheel is going to take some time to get moving, and so it's adding a lot of resistance to the pipe, making it too difficult for the water to flow through this path. Therefore, the water will instead take the path of the reducer because it can flow straight through this and get back to the pump much easier. As the water keeps pushing, the wheel will begin to turn faster and faster until it reaches its maximum speed.
Now the wheel doesn't provide almost any resistance, so the water can flow through this path much easier than the path with the reducer in it. The water will pretty much stop flying through the reducer and it will all now flow through the water wheel. When we turn off the pump, no more water will enter the system, but the water wheel is going so fast, it can't just stop, it has inertia.
As it keeps rotating, it will now push the water and acts like a pump. The water will flow around the loop back on itself until the resistance in the pipes and the reducer slows the water down enough that the wheel stops spinning. We can, therefore, turn the pump on and off, and the water wheel will keep the water moving for a short duration during these interruptions.
We get a very similar scenario when we connect an inductor in parallel with a resistive load, such as a lamp. This is the same circuit as we just saw, but I've just wired it more neatly. When we power the circuit, the electrons are going to first flow through the lamp and power it.
Very little current will flow through the inductor because of its resistance, at first, is too large. The resistance will reduce and allow more current to flow. Eventually, the inductor provides nearly no resistance, so the electrons will prefer to take this path back to the power source rather than through the lamp, so the lamp will turn off.
When we disconnect the power supply, the inductor is going to continue pushing electrons around in a loop and through the lamp until the resistance dissipates the energy. So, what's happening in the inductor for it to act like this? Well, when we pass electrical current through a wire, the wire will generate a magnetic field around it.
We can actually see this magnetic field by placing compasses around the wire. When we pass a current through the wire, the compasses will move and align with the magnetic field. When we reverse the direction of the current, the magnetic field reverses, and so the compasses will also reverse direction to align with this.
The more current we pass through the wire, the larger the magnetic field becomes. When we wrap the wire into a coil, each wire again produces a magnetic field but now it will all merge together and form one large, more powerful magnetic field. We can see the magnetic field of a magnet just by sprinkling some iron filings over the magnet, which will reveal the magnetic flux lines.
When the electricity supply is off, no magnetic field exists, but when we connect the power supply, current will begin to flow through the coil, so our magnetic field will begin to form and increase in size, up to its maximum. The magnetic field is storing energy. When the power is cut, the magnetic field will begin to collapse, and so the magnetic field will be converted into electrical energy and this pushes the electrons along.
In reality, it's going to happen incredibly fast. I've just slowed these animations down to make it easier to see and understand. So, why does it do this?
Well, inductors don't like changing current; they want everything to remain the same. When the current increases, they try to stop it with an opposing force. When the current decreases, they try to stop it by pushing electrons out to try and keep it the way it was.
So, when the circuit goes from off to on, there will be a change in current, it has increased. The inductor is going to try to stop this, and so it creates an opposing force and there's a back EMF, or electromotive force. This back EMF opposes the force which created it.
In this case, that's the current flowing through the inductor from the battery. Some current is still going to flow through, though, and as it does, it generates a magnetic field, which will gradually increase. As it increases, more and more current will flow through the inductor and the back EMF will eventually fade away.
The magnetic field will reach its maximum and the current stabilizes. The inductor no longer resists the flow of current and acts like a normal piece of wire. This creates a very easy path for the electrons to flow back to the battery, much easier than flowing through the lamp.
So, the electrons will flow through the inductor and the lamp will no longer shine. When we cut the power, the inductor realizes that there has been a reduction in current. It doesn't like this and tries to keep it constant, so it's going to push electrons out and try to stabilize it.
This will power the light up. Remember, the magnetic field has stored energy from the electrons flowing through it, and it will convert this back into electrical energy to try and stabilize the current flow. But the magnetic field will only exist when the current passes through the wire, and so, as the current decreases from the resistance of the circuit, the magnetic field collapses until it no longer provides any power.
If we connected a resistor and an inductor in separate circuits to an oscilloscope, then we can visually see the effects. When no current flows, the line is constant and flat at zero, but when we pass current through the resistor, we get an instant vertical plot straight up, and then it flat-line continues at the certain value. But when we connect an inductor and pass current through it, it will not instantly rise up, it will gradually increase and form a curved profile, eventually continuing at a flat rate.
When we stop the current flowing through the resistor, it, again, instantly drops and we get this sudden vertical line back down to zero, but when we stop the current through the inductor, the current continues and we get another curved profile down to zero. This shows us how the inductor resist the initial increase and also tries to prevent the decrease. By the way, we've covered electrical current in detail in a previous video.
Do check that out, link's down below. What do inductors look like? Inductors in circuit boards will look something like this, basically, just some copper wire wrapped around a cylinder or a ring.
We do get some other designs, which have some casing over. This casing is usually to shield the magnetic field and prevent this from interfering with other components. We will see inductors represented on engineering drawings with symbols like these.
Something to remember is that everything with a coiled wire will act as an inductor. That includes motors, transformers, and relays. So, what do we use inductors for?
We use them in boost converters to increase the DC output voltage while decreasing the current. We can use them to choke an AC supplier and only allow DC to pass. We can use them to filter and separate different frequencies, and obviously, we also use them for transformers, motors, and relays.
How do we measure inductance? We measure the inductance of an inductor in the unit of Henry with a capital H. The larger the number, the higher the inductance.
The higher the inductance, the more energy we can store and provide. It will also take longer for the magnetic field to build and the back EMF will take longer to overcome. You can't measure inductance with a standard multimeter, although you can get some models with this function built-in, but it won't give you the most accurate results.
That might be okay for you, it depends on what you're using it for. To measure inductance accurately, we need to use an RLC meter. We simply connect the inductor to the unit and it will run a quick test to measure the values.
Okay, guys, that's it for this video, but to continue your learning, then check out one of the videos on-screen now and I'll catch you there for the next lesson. Don't forget to follow us on Facebook, Twitter, Instagram, as well as TheEngineeringMindset. com.
