# Effect of EMF in a wire as opposed to a metal chassis?

• Planobilly
In summary, when a wire with a pulsating DC current is placed near another wire or a metal chassis, the expanding and contracting magnetic field induces a current into the second wire or the chassis. This effect is known as an eddy current and can generate heat and electromagnetic forces. The current induced in the chassis will be lower than in a single parallel wire due to its larger area and lower resistance. At radio frequencies, a conductive chassis acts as a mirror, causing the induced current in a third wire to be less than when only the first wire is present.
Planobilly
Hi,
Consider a wire with a pulsating DC current next to another wire. The expanding and contraction magnetic field induces a current into the second wire.

Consider the same but in the second case we have a metal chassis. I assume the same magnetic field is inducing a current into the chassis.

Is the induced current dissipated as a function of the large metal chassis and if so how? Are there other considerations?

Thanks,

Billy

The effect is usually called a eddy current. Pulsating DC is no longer simply DC, it has a fundamental component and harmonics. For a non-zero conductance it generates heat and electromagnetic forces.

Last edited:
davenn
Planobilly said:
Consider the same but in the second case we have a metal chassis. I assume the same magnetic field is inducing a current into the chassis.
nsaspook said:
The effect is usually called a eddy current.
yes, think, iron core of a transformer

Planobilly said:
Is the induced current dissipated as a function of the large metal chassis and if so how?
The same current will be induced in the chassis as in a single parallel wire. But the relatively large area of the chassis means that it has a much lower resistance than a wire, so Ohms law says a much lower voltage difference will appear along the chassis than would appear along a parallel wire.

At radio frequencies a conductive chassis makes an excellent mirror. The current in a wire near the “ground plane” sees it's own reflection behind that reflective surface, but with a current flowing in the reverse direction.

A “third” wire near a ground plane will be affected by both the “first” wire and by it's reflection with the opposite direction current. The current induced in a third wire will therefore be less in the presence of the chassis than with the first wire alone.

Planobilly and Bandit127

## 1. What is EMF and how does it affect a wire?

EMF stands for electromagnetic force, which is the force that causes electrically charged particles to move. In a wire, the flow of electrons creates an EMF which can be measured as voltage. This EMF can cause the wire to heat up and potentially damage the wire or any connected devices.

## 2. How does the effect of EMF differ in a wire compared to a metal chassis?

In a wire, the EMF is primarily caused by the flow of electrons. In a metal chassis, the EMF can also be caused by magnetic fields or induced currents. Additionally, the metal chassis may have a larger surface area for heat dissipation, reducing the potential for damage from EMF.

## 3. What are the potential risks associated with EMF in a wire?

The primary risk associated with EMF in a wire is overheating and damage to the wire or connected devices. This can lead to electrical fires or failure of electronic equipment. In extreme cases, exposure to high levels of EMF can also pose health risks to humans.

## 4. How can the effect of EMF in a wire be minimized?

To minimize the effect of EMF in a wire, proper insulation and grounding techniques can be used. Using thicker wires can also reduce the resistance and therefore the amount of EMF generated. Shielding materials can also be used to block or redirect EMF.

## 5. Are there any regulations or standards for EMF levels in wires and metal chassis?

Yes, there are regulations and standards set by organizations such as the International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronics Engineers (IEEE) for safe levels of EMF in wires and metal chassis. These standards vary depending on the application and location of the wire or chassis.

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