# Electric Field Strength H Units - Ampere Turns/Meter?

• ultimateguy
In summary, the units of the electric field strength H are ampere per meter in the SI system, or Oersted (Oe) in the older cgs system. In the gaussian system, H and magnetic induction B have the same units, making it easier to plot a magnetic hysteresis curve. However, there is a debate over whether B or H should be called the magnetic field. Mel Schwartz, a Nobel prize winner, argued that B should be considered the fundamental field and H a subsidiary artifact.
ultimateguy
What are the units of the electric field strength H? I know that H = NI/L for a solenoid and I'm wondering if there is any condensed unit or if it is just ampere turns per meter.

ultimateguy said:
What are the units of the electric field strength H? I know that H = NI/L for a solenoid and I'm wondering if there is any condensed unit or if it is just ampere turns per meter.

$\mathbbs{H}$ is the symbol used for magnetic field strength and has SI units of teslas.

The magnetic field $\mathbbs{H}$ has units of amp/meter in the SI system, with no special name attached. In the older cgs units it was called an Oersted (abbreviated Oe). The mention of teslas in the previous post refers to magnetic induction $\mathbbs{B}$. $\mathbbs{B}$ is now commonly called magnetic field, leading to confusion.

Thanks for the info. I was wondering because I'm plotting a magnetic hysteresis curve and have B vs. H and I didn't think they both had the same units.

ultimateguy said:
Thanks for the info. I was wondering because I'm plotting a magnetic hysteresis curve and have B vs. H and I didn't think they both had the same units.
That is one of the virtues of the "old" gaussian system.
There B and H can have the same units so the hysteresis curve has a simple meaning. The gaussian unit for H is called "Oersted" for historical reasons, but it really is the same as the unit "gauss".

Meir Achuz said:
That is one of the virtues of the "old" gaussian system.
There B and H can have the same units so the hysteresis curve has a simple meaning.
More like a vice! I always wondered why people seemed so flippant about interchanging the magnetic flux and field. More often than not, you'll find B being referred to as the field! I guess this was the reason.

Meir Achuz said:
That is one of the virtues of the "old" gaussian system.
There B and H can have the same units so the hysteresis curve has a simple meaning. The gaussian unit for H is called "Oersted" for historical reasons, but it really is the same as the unit "gauss".
Agreed, this is a nice feature of Gaussian units.

ObsessiveMathsFreak said:
More like a vice! I always wondered why people seemed so flippant about interchanging the magnetic flux and field. More often than not, you'll find B being referred to as the field! I guess this was the reason.

You mean magnetic induction and field (flux is yet another quantity). Yes, many writers call B the magnetic field without explanation or comment. Mel Schwartz, in "Principles of Electrodynamics" (1972), is one of the few who are up front in addressing this:
At this point we interject a small bit of philosophy. It is customary to call B the magnetic induction and H the magnetic field strength. We reject this custom inasmuch as B is the truly fundamental field and H is a subsidiary artifact. We shall call B the magnetic field and leave the reader to deal with H as he pleases.

marcusl said:
Agreed, this is a nice feature of Gaussian units.

You mean magnetic induction and field (flux is yet another quantity). Yes, many writers call B the magnetic field without explanation or comment. Mel Schwartz, in "Principles of Electrodynamics" (1972), is one of the few who are up front in addressing this:
At this point we interject a small bit of philosophy. It is customary to call B the magnetic induction and H the magnetic field strength. We reject this custom inasmuch as B is the truly fundamental field and H is a subsidiary artifact. We shall call B the magnetic field and leave the reader to deal with H as he pleases.
Mel deserves his Nobel prize for that sentence alone.

Edit: For that and more. I was friends with a couple of Mel's grad students working on the pi-mu atom, and had the chance to speak with him a few times. He was not only sharp, but was very nice as well. His accent (Bronx?) and mannerisms reminded me a little of Feynman. I was thrilled when I heard he had won the prize.

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## 1. What is the unit for electric field strength?

The unit for electric field strength is Ampere Turns/Meter, also known as A/m or A·m-1.

## 2. How is electric field strength measured?

Electric field strength is measured by determining the force exerted on a unit positive charge placed in the electric field. This force is then divided by the charge to give the strength of the field.

## 3. What is the relationship between electric field strength and distance?

The electric field strength is inversely proportional to the square of the distance from the source of the field. This means that as the distance increases, the electric field strength decreases.

## 4. Can electric field strength be negative?

Yes, electric field strength can be negative. It indicates that the direction of the field is opposite to the direction of the electric current. This can occur in situations where the current is flowing in a circular or opposite direction.

## 5. How does the number of turns in a coil affect electric field strength?

The number of turns in a coil is directly proportional to the electric field strength. This means that increasing the number of turns will increase the strength of the field, while decreasing the number of turns will decrease the strength of the field.

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