How Inductors Work - The Learning Circuit

the following program is brought to you by element 14 the electronic design community where you can connect and collaborate with top engineers from around the world join now at element14.com hi and welcome back to the learning circuit I'm Karin and today we're going to learn about inductors an inductor is a coil of wire designed to take advantage of the relationship between magnetism and electricity previously we learned how electricity interacts with a coil of wire to create a magnetic fields when a voltage is applied across a wire the movement of the current through the wire generates magnetic lines of flux when that wire is wrapped into a coil the flux of each turn adds together to form a magnetic fields the size of the magnetic field is proportional to the amount of amps of current flowing through the coil when the current flowing through the wire is constant the voltage potential across the coil matches that of the power supply at this point the coil acts as an electromagnet but that's not all that's going on when the coil is connected to a power source the current increases and the magnetic field expands as power is cut off from the coil the current decreases and the magnetic field collapses inductor coils are resistant to changes in current it takes time for one end of the coil to catch up to the other so when the current changes there's a voltage potential induced across the coil however its polarity is reversed that of the supply voltage and the two voltages oppose each other the inductance of a coil is the degree in speed in which it generates a voltage as a result of a change in current the reverse polarity of the coil lasts until the supply current forces the coils polarity to revert back the time it takes for the supply current to change the coil current is determined by the coils inductance the higher the inductance the longer it takes for the current to change the supply current will eventually cause the current within the inductor to equalize and their polarities will be the same at this point the current is constant the magnetic field is stabilized and the current flows freely through the inductor in the magnetism episode we learned what factors affect the amount of flux generated by a coil since magnetic flux influences inductance inductance is affected by those same factors the number of turns in the coil the amperage of the current and the permeability of the core all factor into inductance additionally unlike with flux the diameter of the coil is a factor inductance is measured in henries an inductance of one Henry represents a potential difference of one volt across an inductor within which the current increases or decreases at the rate of one amp per second like with farad's the measurement of capacitance 1 Henry is quite large instead inductance is usually measured in militant Riis micro henries or nano Henry's let's look at how inductance is calculated a capital L is used to represent inductance you'll notice that along with the factors we've mentioned number of turns core permeability and diameter or area within the coil average length of the coil is an additional factor in an electromagnet the turns are usually as close together as possible this is not always the case with inductors sometimes the coils are stretched out if you remember how the flux of each turn adds together to create a stronger magnetic field you can understand the correlation the closer together the turns the higher the inductance the more stretched out the lower the inductance well we can use some physical characteristics of the inductor to calculate its theoretical inductance getting a practical measurement requires factoring in time and can only be done with more sophisticated devices and techniques than just connecting it to a common multimeter to determine the rating of an inductor the best place to look is on its product page or datasheet look for a number followed by an H remembering that the measurement will likely be in millihenries micro henries or nano Henry's when inductors are placed in series or parallel their combined inductance can be measured using the same equations as resistors however there is a stipulation that the magnetic fields of the various inductors cannot interact for the equation to be true [Music] let's talk about the different types of inductors the difference is mostly break down to the make up of the core and the shape of the coil we know that the permeability of the core is an important factor in inductance some inductors have what is called an air core some of these are self-supporting being completely empty containing only air others are supported by a material with permeability properties similar to air such as plastic ceramic or other non ferromagnetic materials having a relative permeability rating of one air dissipates almost no energy as heat this means air core inductors are great for high power applications such as RF transmitters amplifiers or tuners however the low permeability of the core means that the inductors have to get quite large relative to their available inductance iron core inductors have a core made up of you guessed it iron iron having a relatively high permeability rating it's capable of increasing inductance by a factor of 100 to 1 million times that of air this requires fewer coil turns to achieve the same inductance allowing these inductors to be much smaller a downside of this type of inductor is that iron cores can experience significant power losses when operated at higher frequencies so they are better suited for low frequency applications such as audio and DC power supply circuits some inductors have ferrite cores farad is an iron product that when used in cores has similar characteristics as iron core inductors ferrite cores are nonmetallic giving them a higher resistance than iron cores and therefore they do not suffer the same power losses at high frequencies this makes ferrite core inductors better suited for higher frequency applications such as computers and telecommunication systems inductors made as straight cylindrical or helical coils are called solenoidal solenoid also refers to a device that converts electrical energy to mechanical energy using a solenoidal inductor the metal core of a solenoid is mobile when the coil is energized the core can be pushed or pulled within the coil some inductors are variable and can be tuned by sliding the ferromagnetic core in or out of the coil this changes the effect of permeability within the coil which is why it's called permeability tuning since a coils magnetic field can extend significantly outside the component it's difficult to keep them from affecting each other one way to minimize the effects of this mutual inductance is by using donut-shaped or toroidal windings because of its shape nearly all the flux produced by the coil remains in the core compared to solenoidal inductors tore roids can have greater inductance values for their size as well as have extremely accurate rated values an alternative method for confining flux is by surrounding a loop shaped coil of wire with a ferromagnetic shell making a pot core pot cores have the advantages of a toroid but can achieve even larger inductances for their size when using abductors in circuits it's important to ensure that the inductor has a path for the current buildup to drain if not provided it'll find its own be it through the air bridging across an open switch or through other components potentially damaging them inductors can be found everywhere they're extremely useful and have a wide variety of applications they're used in so many products that you probably interact with multiple every day one of the most recent innovations is induction charging where you can simply place your cell phone or device on a charging pad and it will charge without needing to be plugged in well thanks for joining me today to talk about inductors do you want to have a new and interesting way to use an inductor in a project tell us about it on the element14 community on element14.com forward slash the learning circuit happy learning [Music]

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Keywords: electronics, hardware, gaming, hacking, mods, weekly, element14, tbhs, benheck, madison, wisconsin, maker, engineering

Id: cP2HBq6DkSc

Length: 8min 5sec (485 seconds)

Published: Wed Jan 16 2019