# Exploring Back EMF - What is the Cause?

• len legare
In summary, back EMF happens when the electromagnetic field of a transformer collapses, sending stored energy back as a spike of power. The power factor of this collapse is slightly less than the initial energy.
len legare
I have always wondered if anyone has ever developed an understanding of why Back EMF happens?

All I know is it happens when the the field inside of a transformer collapses at some low frequency during the collapse of the coil when the transistor shuts off creates a huge spike hundreds of times the supply voltage is created within the coil. is there a new understanding of why this happens?

I appreciate any help in in expanding my knowledge of this phenomena.

Thanks.

len legare said:
I have always wondered if anyone has ever developed an understanding of why Back EMF happens?

All I know is it happens when the the field inside of a transformer collapses at some low frequency during the collapse of the coil when the transistor shuts off creates a huge spike hundreds of times the supply voltage is created within the coil. is there a new understanding of why this happens?

I appreciate any help in in expanding my knowledge of this phenomena.

Thanks.

If I'm not mistaken, it is because the electromagnetic field of the transformer actually stores energy, and when you shutoff the transformer, the electromagnetic field collapses, sending that energy back as a spike of power.

Remember also, that back EMF collapse, regardless of high voltage or not, has a power factor slightly less than that which created it.

## 1. What is back EMF?

Back EMF, or electromotive force, is the voltage that is produced in a coil or conductor when there is a sudden change in current flow. It is essentially a reverse voltage that opposes the change in current flow.

## 2. What causes back EMF?

Back EMF is caused by the magnetic field generated by the changing current in a coil or conductor. When the current changes, the magnetic field collapses and induces a reverse voltage in the conductor.

## 3. How does back EMF affect electronic circuits?

Back EMF can cause problems in electronic circuits, particularly in motors and relays. It can create voltage spikes and interfere with the functioning of the circuit if not properly managed.

## 4. How can back EMF be measured?

Back EMF can be measured using a voltmeter or oscilloscope. The voltage produced by the back EMF can be measured and used to calculate the magnitude of the magnetic field and the current in the conductor.

## 5. How is back EMF used in electronic circuits?

Back EMF is commonly used in electronic circuits to control the speed and direction of motors. By measuring and utilizing the back EMF, the circuit can adjust the current flow to maintain a constant speed or change the direction of the motor.

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