# Induction Strength

#### Waphle_Stomp

Joined Feb 6, 2021
3
I read the other day an article which stated the factors which affected the strength of an induced current being:
• "l"-Length of the conductor in the magnetic field
• "v"-Velocity of the conductor (speed of the rotor)
• "B"-Strength of the electromagnetic field

From that list there's one thing I'm not sure of so I'm asking for clarification.

When it says '"l"-Length of the conductor in the magnetic field', is it being stated:
• the total length of the conductor?, or
• the length of conductor which is directly exposed to the field?

For example, if I had two loops with the following aspects:
one with a diameter of 6", the other 12", and both coils otherwise equal:
• same gauge,
• wound with the same density
• wound in the same direction,
• placed the same distance from the passing magnet
• 1" length of coil by which the magnet passes
• magnet applied with the same velocity
• same field strength.

Would both coils provide the same voltage and current? or would one create more than the other?

Thank you for any clarification.

#### Danko

Joined Nov 22, 2017
1,490
I read the other day an article which stated the factors which affected the strength of an induced current being:
• "l"-Length of the conductor in the magnetic field
• "v"-Velocity of the conductor (speed of the rotor)
• "B"-Strength of the electromagnetic field

From that list there's one thing I'm not sure of so I'm asking for clarification.

When it says '"l"-Length of the conductor in the magnetic field', is it being stated:
• the total length of the conductor?, or
• the length of conductor which is directly exposed to the field?

For example, if I had two loops with the following aspects:
one with a diameter of 6", the other 12", and both coils otherwise equal:
• same gauge,
• wound with the same density
• wound in the same direction,
• placed the same distance from the passing magnet
• 1" length of coil by which the magnet passes
• magnet applied with the same velocity
• same field strength.

Would both coils provide the same voltage and current? or would one create more than the other?

Thank you for any clarification.
1. Only length affected by magnetic field is counted.
2. If number of turns in coils equal, then induced voltages equal too.

Last edited:
• DickCappels

#### MisterBill2

Joined Jan 23, 2018
13,712
The relationships given are not the exact definitions. In addition, the edge of the magnetic flux is not a sharp line. The exact description for the voltage generated by a changing magnetic flux passing through the conductor is "per incremental length", which is rather tedious to deal with. Functionally, every tiny bit of length with the varying flux passing through generates a voltage. so the correct answe is that probably the voltages would be close but not the same because the exact amount of flux would not be exactly the same. But if that flux were perfectly uniform then the voltages should be the same. I can pull out an old college physics book and possibly provide the exact calculus, but the TS can probably locate a similar text closer at hand. An old book will be adequate, the relationships have not changed.

#### Waphle_Stomp

Joined Feb 6, 2021
3
The relationships given are not the exact definitions. In addition, the edge of the magnetic flux is not a sharp line. The exact description for the voltage generated by a changing magnetic flux passing through the conductor is "per incremental length", which is rather tedious to deal with. Functionally, every tiny bit of length with the varying flux passing through generates a voltage. so the correct answe is that probably the voltages would be close but not the same because the exact amount of flux would not be exactly the same. But if that flux were perfectly uniform then the voltages should be the same. I can pull out an old college physics book and possibly provide the exact calculus, but the TS can probably locate a similar text closer at hand. An old book will be adequate, the relationships have not changed.
So, then could I reasonably surmise the mentioned article's author was referring to "Length of the conductor in the magnetic field" being the number of turns, and not merely the length of the coil?

Also, if the length is actually somewhat irrelevant then one would likely be better off building motors or generators with shorter coils, providing the machine can adequately supply velocity and flux strength.

#### Waphle_Stomp

Joined Feb 6, 2021
3
1. Only length affected by magnetic field is counted.
2. If number of turns in coils equal, then induced voltages equal too.