A quick cheat sheet on back emf in under 5 mins

A quick review on how spinning electric motors will generate a voltage that hinder its rate of turn.

LIKE and SHARE with your peers. And please add a COMMENT to let me know I have helped you.

Physics High is committed to producing content that teaches physics concepts at a level a high schooler can understand.

As well as this I produce a podcast series called Deep Impact - interviews with science communicators as to what they do, what drives them to communicate their craft
You will find these on the channel and also on podcast sites such as Spotify, Apple and Google podcasts

👥 Social
---------------------------------------------------------
Follow me on
facebook: @physicshigh
twitter: @physicshigh
Instagram: @physicshigh

[jibraanrasheed]

I love this guy, his explanation is simple and easy to understand. Literally tutoring me 3 days before my hsc exam 😭

[jxmiie]

thank you for explaining why the current can't reach zero at operating speed. you're the only one who has explained it properly

[alex.e.jtulkens]

This helped me so much. Thank you for the clear explanation

[spitfire]

Here's a plan. As the rotor magnet sweeps through the stator coil field, producing forward EMF in the stator coil, harvest the back EMF by disruption, breaking the circuit at the 90° top dead center and you have what you refer to as high negative fleeting back voltage in the negative side. Since it is not accompanied by any current, it is useless qnd in fact problematic in the electrical industry. So, where is the current? It is still on the other side of the gap in the coil you created by the disruption, giving the motor / generator a real hard time. This is because of the time lag. You also have to harvest the back current. The reason we have this effect, is because the BEMF is merely 90° out of phase with the voltage and is locked out and prevented to get to the voltage, all though it wants to, but can't. You can wait till it jumps the gap, but then the voltage is too high and will damage your MOSFETs or othe devices you use to create the gap. Two things need to be done.
1) get the amps back across the disrupted gap
2) get the negative back amps in phase with the its negative voltage, which will create a powerfull negative EMF wich can be used in the most amazing way. And here's the solution, there's a name for it in fact, its called power factor correction. And I believe I have the perfect solution how to achieve this. And Im sure you caught on now as well .😊❤

[nothingandmorenothing]

This is so, so well made! Thank you so much! I hope you reach as many people as possible to help them all!

[jimmybrad]

energy (joules) is power-time (watt-seconds), not power (watts) in case anyone's wondering :P

[jjqformerlyjailbreak]

Ok let me explain my question before I ask it please? Back EMFs are always explained as dangerous and bad for circuits, but can’t we use this back EMF to our advantage by storing the reverse charge then feeding it back into the circuit after inverting it?

I’m starting to wrap my head around circuitry, and want to explore what can be done with back EMFs.

[v_]

a moment of respect for this guy writing in reverse

[concernkid]

left hand rule for motors and right hand rule for generators

[thunchan]

1:05 motor rotation direction by Fleming's left hand rule, not Fleming's right hand rule.

[fromisheon]

Why low back emf causes the resistance reduced?

[waterfuel]

####!!Are you saying that the back EMF does not go through anode of Led, and is a negative flow of current? (not positive voltage)?...???

[fadi]

but how you make it spin faster in the first place ? so that the rate of changing flux is higher ? you need to increase the current right ? then how does it become lower ?

[paulwyleciol]

actually I came here to understand, why the motor turns quicker, when the (permanent) magnets are given more and more distance??? 😢 Could you please tell me?

[yezan]

Sir the back emf has nothing to do w the supply voltage, sure if we do a kvl loop we can show how emf is equal to series resistance voltage drop + supply and also the emf will attempt to bring up this supply voltage…back emf is a function of the motor parameters such as Ke of motor and change rate of magnetic flux like you mentioned through the loop of wire..the statement that ‘emf cannot exceed supply voltage’ is simply not true as often times it does. If you are not to clamp a inductive load such as a relay for example w a anti parallel diode the relay coil generated voltage spike can certainly be above supply voltage and other components ratings damaging them…look into 4 motor quadrants, in quad 2 and 4 motor is a generator supplying a load to the ‘supply’ as current sinks to it as voltage is larger…also energy is not equal to VI…Power = Energy/time = VI….sorry good video otherwise..