1

Negligible Electromagnetic Shielding of MED from Near Static to 10

Megahertz Frequencies

Thomas A. Manz,* Jacob R. Wright, and Xaviar F. Enriquez

Department of Chemical & Materials Engineering, New Mexico State University, Las Cruces,

NM 88001

______________________________________________________________________________

Abstract:

An effect discovered by Manz (J. Space Mixing, 6 (2016) 1-17.) produces a net attractive

rather than repulsive force between two like-signed macroscopic static charge distributions. In

this work, we constructed electric circuits and measured the response of a Manz effect device

(MED) to applied electromagnetic waves from near static to 10 megahertz frequencies. We

found no appreciable electromagnetic shielding over this frequency range. This result is not

completely surprising, because previous experiments and theoretical analysis suggested

electromagnetic scattering or reflection by a MED may occur primarily within the infrared and

microwave frequency ranges. We recommend that follow-up experiments be performed to

measure the response to applied electromagnetic waves at these higher frequencies. We also

constructed electric circuits and performed experiments to quantify the net charge. Our

measurements were not sensitive enough to measure the final net charge residing on the MED,

but they were sensitive enough to reliably measure the initial static charge of the friction rods

used to charge the device. We recommend that more sensitive follow-up experiments be

performed to measure the final net charge residing on the MED.

______________________________________________________________________________

keywords: static electricity, physics, electromagnetism, inductors, electromagnetic shielding

1. Introduction

A newly discovered effect produces a net attractive force between a pair of metallized

dielectric foils containing like-signed electrostatic charges.[1] This effect is highly unusual,

because its force is in the direction opposite to that predicted by Coulomb’s Law. Coulomb’s

Law predicts repulsion between like-signed electrostatic charges.[2] This attractive force was

attributed to the scattering or reflection of electromagnetic waves off the electrostatic potential

kink that occurs at the confined charge layer in each of the two roughly parallel plates.[1]

This effect is completely different than the effect producing attraction between like-

charged small polymer spheres in aqueous media that arises from the build-up of counter ions in

the space between the charged polymer spheres.[3] Specifically, experiments by Nagornyak et al.

showed “an accumulation of protons was found between negatively charged spheres, whereas

between positively charged spheres the intermediate zone contained OH− groups.”[3] The small

polymer spheres moved towards each other in aqueous media, because the two negatively

charged spheres were attracted to the protons between them, and the two positively charged

spheres were attracted to the OH- ions between them.[3] When this build-up of charged ions is

taken into account, the direction of net force between the small charged polymer spheres in

aqueous media is in the direction predicted by Coulomb’s Law.

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In contrast, the net force direction in a MED opposes that predicted by Coulomb’s Law.

To understand how unusual this is, consider the following statement from a popular physics

textbook: “Coulomb’s law has survived every experimental test, no exceptions to it having ever

been found. It holds deep within the atom, correctly describing the force between the positively

charged nucleus and each extranuclear electron. Although classical Newtonian mechanics fails in

that realm—where it is replaced by quantum physics—Coulomb’s simple law continues to give

correct answers. This law also correctly accounts for the forces that bind atoms together to form

molecules and the forces that bind atoms or molecules together to form solids or liquids.”[2, pp.

537-538] This statement was published in 1988, before the discovery of the MED.

The establishment of this effect as a fundamental modification of the electrostatic

interaction derives from the observation that a unified scaling relation is maintained.[1]

Specifically, the attractive force between parallel plates exhibiting this effect was theoretically

shown to scale proportional to the charge-density squared, which is the same scaling behavior

(but opposite in direction and possibly different in magnitude) to that theoretically predicted by

Coulomb’s Law.[1] The experimental evidence for this is that the attractive force between the

two plates does not change rapidly as the distance between the two plates is varied as long as the

angle between the two plates does not cross a critical threshold.[1] This is precisely the form of

interaction force predicted for two infinite, parallel, uniformly charged plates when the

underlying interaction force scales inversely proportional to the squared distance between point-

like charge carriers.[1] Hence, the same net charge carriers and the same kind of inverse squared

force law acts to produce the Coulombic force and this effect, except the direction is reversed

and the magnitude may be altered.

The basic operation of a MED is shown in Video 1, Video 2, and Figure 1. An

electroscope with hanging metalized dielectric foil leaves begins with the leaves in an uncharged

state and hanging parallel as shown in Figure 1A. As explained in a previous article [1], these

metalized dielectric foil leaves consist of a thin gold layer covering one side of a thin aliminum

layer and coated on both sides with plastic. In Video 1, the electroscope is charged with a

negatively charged plastic friction rod to make the electroscope leaves repel (Figure 1B). The

electroscope terminal is then grounded by touching it with a finger to produce the attractive,

bound state (Figure 1C and Video 1). Video 2 then begins with the electroscope leaves in the

attractive, bound state (Figure 1C). A negatively charged plastic friction rod is then touched to

the electroscope terminal to produce a combined attractive-repulsive state, in which attraction

occurs between the centers of the two leaves and repulsion occurs between their bottom edges

(Figure 1D and Video 2). The electroscope terminal is grounded with a finger to remove the

repulsive component and return the device to the fully attractive state (Figure 1C and Video 2).

The rest of this article is organized as following. Section 2 describes the net charge

measurements. We measured the net charges of two charged friction rods that were used to

charge the device. We use calculations to explain why our experiments were not sensitive

enough to accurately quantify the net charge remaining on the activated MED. Section 3

describes the electromagnetic shielding measurements from near static to 10 megahertz

frequencies. The activated MED did not exhibit any appreciable electromagnetic shielding over

this frequency range. Section 4 presents our conclusions and recommendations.

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Video 1 (6 seconds): Video showing

formation of the attractive state (Figure 1C).

Sequence: The electroscope is charged with

a negatively charged plastic rod to make the

leaves repel each other (Figure 1B). Then

the electroscope terminal is grounded to

produce the state in which the two leaves

attract each other (Figure 1C).

Video 2 (4 seconds): Video showing the

attractive state exists between two leaves

having the same signs of net charges (Figure

1D). Sequence: The leaves are in the

attractive state (Figure 1B). Additional

charge is then added by touching a

negatively charged plastic rod to the

electroscope terminal to produce a combined

attractive/repulsive state (Figure 1D). The

electroscope terminal is then grounded to

restore the purely attractive state (Figure

1C).

Figure 1: A pair of thin films containing an aluminum layer and a gold layer, with a plastic

coating on both sides. States (A) to (E) represents a sequence of steps. (A) Uncharged foils

hanging parallel in Earth’s gravitational field. Charging the leaves produces state (B) in which

the leaves repel each other. Grounding the electroscope terminal produces the attractive state

shown in (C). Adding a small amount of additional like charge to the leaves produces repulsion

in one part of the leaves but not enough to overcome the attraction: (D) repulsive at bottom and

attractive in middle or (E) repulsive in middle and attractive at bottom. Adding a higher amount

of like charge causes the repulsion to overcome the attraction and leads to state (B).

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2. Net Charge Measurements

Figure 2 illustrates an electric circuit we used to measure the net charges of objects. This

circuit contained a metal conducting pan placed on an electrical insulator (e.g., glass). The

charged test object was lowered into the pan but did not touch the pan. At this time, the pan was

connected to ground using a conducting metal wire. Grounding the pan caused a static charge of

similar magnitude but opposite sign to that of the enclosed test object to accumulate on the pan

walls. After disconnecting the grounding wire, the test object was raised high above the pan. At

this time, the two terminals of capacitor C1 were shorted out by connecting them together with a

metal object and also connected to ground. Then, only one side of the capacitor C1 was left

connected to ground and the other side of capacitor C1 was electrically connected to the metal

pan through resistor R1. Then the voltage across C1 was measured to compute the charge. The

calculated charge of the test object is given by Q = -(C1)*voltage. (The minus sign occurs

because a positively charged test object attracts a negative charge in the metal pan.)

The capacitance C1 must be much larger than the pan’s capacitance to ensure most of the

charge is transferred to C1. The capacitance of an isolated conducting sphere equals 40R,[2]

which gives C = 10-11 farad for a sphere of radius of 0.1 m. We used a collecting capacitor of

value C1 = 4.7×10-7 farad. Estimating the capacitance of the metal pan to be approximately 10-11

farad, this means that only approximately 10-11/(4.7×10-7) = 2.4×10-5 fraction of the static charge

remains on the metal pan after it has been connected to capacitor C1. In other words, essentially

all of the static charge gets transferred from the metal pan to capacitor C1.

C1 must also be small enough to ensure a measurable voltage. The voltmeter we used

could measure voltages reliably down to 0.1 to 1 mV. This means the smallest net charge that

could be measured with this electric circuit was on the order of 4.7×10-11 to 4.7×10-10 Coulomb.

Also, the time constant R1*C1 must be a small fraction of a second to provide rapid

collection of the static charge onto the capacitor C1 when the metal pan is connected to it. Using

a 1000 ohm resistor R1 gives a time constant of 1000(4.7×10-7) = 0.47 milliseconds, which is

sufficiently rapid. The internal resistance of the voltmeter should be sufficiently high to provide

a slow discharge of the capacitor through the connected voltmeter. We used a Hung Chang HC-

303TU digital multimeter to measure voltages on a 200 mV scale with a resolution of 0.1 mV.

We observed a time constant for capacitor discharge through the voltmeter of a few seconds (~3

seconds), which means the internal resistance of the multimeter during these voltage

measurements was ~3 s/(4.7×10-7 farad) = 106 to 107 ohm.

As shown above, the smallest net charge that could be measured with this electric circuit

was on the order of 4.7×10-11 to 4.7×10-10 Coulomb. Unfortunately, this does not provide enough

sensitivity to measure the net charge residing on the charged leaves in the activated attractive

state. For purposes of illustration, suppose the charged leaves before being grounded (i.e., in the

state shown in Figure 1B) produced an electric field that equals one-tenth the dielectric strength

of air. (The dielectric strength of air is approximately 3×106 V/m.[2]) This corresponds to a

surface charge density of 12 5 6 202 E 2 8.85 10 3 10 5 10 Coul / m . The charged area on the leaves was approximately 1 cm × 1 cm = 10-4 m2. This would provide a total net

charge (for leaves in the state shown in Figure 1B) of approximately 6 2 4 25 10 Coul / m 10 m 105 10 Coul , which is just within the detection threshold of our electric circuit. We estimate

that the net charge residing on the leaves decreased by an order of magnitude when the leaves in

the state shown in Figure 1B were grounded through the electroscope terminal to produce the

activated attractive state shown in Figure 1C. This puts the estimated net charge magnitude of the

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charged leaves in the activated attractive state (Figure 1C) at ~5×10-11 Coul, at the low end of the

detection limit of our electric circuit.

In an attempt to increase the measurement sensitivity, we averaged the voltage

measurements over numerous experiments for each charged object. We also tried to build up the

collection of charge onto the capacitor C1 by repeatedly charging the metal pan (by lowering the

test object into the pan and grounding it) and then connecting the metal pan to capacitor C1.

These attempts to improve the measurement sensitivity gave mixed results. We were able to

measure net charges on the leaves in the 10-11 to 10-10 Coul range, but the repeatability of the

experiments was extremely poor. Specifically, the measured net charge often varied by a factor

of three or four, and occasionally even the sign of the net charge varied between repeat

measurements. One may expect the measurement sensitivity could be improved by decreasing

the capacitance of C1, but this also causes the discharge time through the voltmeter to be

increased. In fact, we tried a smaller C1 value, but the increased discharge rate prevented any

increase in measurement sensitivity. We also noticed that one should avoid wearing clothing

such as sweaters that builds up static electricity that can interfere with these static charge

measurements.

Figure 2: Circuit diagram for measuring the charge of an object. A metal conducting pan is

placed on an electrical insulator. The charged object is lowered using a thin insulating string into

the pan without touching the pan. The pan is then grounded. Then the contact with ground is

broken. The charged object is then removed from the pan. The capacitor C1 is discharged to

ground. The pan is then connected to the capacitor C1 through resistor R1. The pan is then

disconnected from the circuit. Then the voltage across C1 is measured to compute the charge.

In spite of these measurement limitations, we noticed a trend that the sign of the net

charge remaining on the charged leaves in the activated attractive state (Figure 1C) after

grounding the electroscope terminal was nearly always the same as the sign of initial charging

(Figure 1B). Specifically, charging the electroscope terminal with a negatively charged friction

rod and then grounding the electroscope terminal produced an activated charged state (Figure

1C) with negative net charge. Charging the electroscope terminal with a positively charged

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friction rod and then grounding the electroscope terminal produced an activated charged state

(analogous to Figure 1C) with positive net charge.

As shown in Table 1, we reliably measured the net charges of the charged friction rods.

First, we performed several calibration experiments that showed the net charge of the friction rod

measured via the metal pan circuit shown in Figure 2 is comparable to the charge magnitude that

resulted from directly contact wiping the charge off the rod onto the capacitor. (In contact

wiping, the charged rod was discharged onto the non-grounded leg of the capacitor by directly

wiping the rod onto to the corresponding capacitor terminal.) This shows the metal pan circuit of

Figure 2 produces reliable measurements of the friction rod charges. Next, we performed several

charge measurements using this metal pan circuit. As shown in Table 1, the plastic rod rubbed

with rabbit fur acquired a static charge of -19 (avg.) ± 4 (st. dev.) nanocoulombs over five

replicates. This corresponds to electrons being transferred from the rabbit fur to the plastic rod.

As shown in Table 1, the glass rod rubbed with wool cloth acquired a static charge of +19 (avg.)

± 9 (st. dev.) nanocoulombs over six replicates. This corresponds to electrons being transferred

from the glass rod to the wool cloth.

Table 1: Experiments measuring net charges of charged rods.

Exp Rod Used cloth

Measured

Voltage

(mV)

Calculated

Charge

Coulombs

1 plastic rabbit fur 55 -26 × 10-9

2 plastic rabbit fur 29 -14 × 10-9

3 plastic rabbit fur 40 -19 × 10-9

4 plastic rabbit fur 45 -21 × 10-9

5 plastic rabbit fur 37 -17 × 10-9

experiments 1 to 5: -19 (avg.) ± 4 (st. dev.) nanocoulombs

6 glass wool -80 38 × 10-9

7 glass wool -37 17 × 10-9

8 glass wool -26 12 × 10-9

9 glass wool -28 13 × 10-9

10 glass wool -38 18 × 10-9

11 glass wool -36 17 × 10-9

experiments 6 to 11: +19 (avg.) ± 9 (st. dev.) nanocoulombs

3. Electromagnetic Shielding Measurements

Figure 3 shows a schematic diagram of the electric circuit we used for the

electromagnetic shielding measurements. Figure 4 shows a photograph of the experimental

setup. Both the emitter and detector used were 500 millihenry wire wound inductors, with the

emitter connected to the function generator, and the receiver connected to the oscilloscope. The

emitter broadcast a sinusoidal electromagnetic wave of chosen frequency and amplitude. The

receiver detected both the amplitude and frequency of the received signal. The emitting and

receiving coils were located along a common axis with a 3.5 cm air gap between the two coils.

The object to be tested for electromagnetic shielding effects was placed midway between the

emitting and receiving coils without touching either coil.

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Figure 3: Circuit diagram of the shielding capabilities test experiment.

Figure 4: Photograph of the experimental setup for testing the electromagnetic shielding

capabilities. The oscilloscope is shown on the left. The function generator is shown on the right.

The emitter and receiver coils are shown in the front mounted to a piece of foam.

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Results are shown in Figure 5, Figure 6, and Table 2. Experiments were performed at 40

kHz, 46 kHz, and 10 MHz with a function generator signal with 20 volts peak-to-peak. For each

of these experiments, the frequency detected in the receiving coil was the same as that driving

the emitting coil. As expected, the peak-to-peak voltage measured in the receiving coil by the

oscilloscope was smaller than that of the function generator driving the emitting coil. An iron

plate gave a strong shielding effect, dropping the receiving coil peak-to-peak voltage from 1.7 ±

0.1 (no object) to 0.6 ± 0.1 volts (with Fe plate). Aluminum foil showed a modest shielding

effect by reducing the measured peak-to-peak voltage by about 10% at 46 kHz and 10 MHz.

Figure 5: Shielding test waveforms at 46 kHz. Top left: Nothing between inductors. Top right:

Uncharged metallized foils between inductors. Middle left: Leaves in attractive state charged

with a glass rod. Middle right: Leaves in attractive state charged with a plastic rod. Bottom:

Single sheet of aluminum foil (cut to the same length and width as the leaves) between inductors.

In Table 2, the column labeled ‘charge sign’ indicates whether the test object is

uncharged (‘0’) or has been charged with a positive (‘+’) or negative (‘-’) static charge. The

column labeled ‘excess charge’ indicates whether the test object has been ungrounded (‘Y’) or

grounded (‘N’), where grounded leaves means that the electroscope terminal has been grounded.

Please keep in mind that (i) ‘test object = leaves’ with ‘charge sign = 0’ and ‘excess charge = N’

corresponds to the state shown in Figure 1A, (ii) ‘test object = leaves’ with ‘charge sign = -’ and

‘excess charge = N’ corresponds to the activated attractive state shown in Figure 1C with

negative charging, (iii) ‘test object = leaves’ with ‘charge sign = +’ and ‘excess charge = N’

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corresponds to the activated attractive state analogous to Figure 1C with positive charging, and

(iv) ‘test object = leaves’ with ‘charge sign = -’ and ‘excess charge = Y’ corresponds to the

combined attractive-repulsive state shown in Figure 1D with negative charging. Irrespective of

their charge state, the pair of electroscope leaves showed no electromagnetic shielding effects at

40 kHz, 46 kHz, and 10 MHz.

Figure 6: Shielding test waveforms at 10 MHz. Top left: Nothing between inductors. Top right:

Uncharged metallized foils between inductors. Middle left: Leaves in attractive state charged

with a glass rod. Middle right: Leaves in attractive state charged with a plastic rod. Bottom:

Single sheet of aluminum foil (cut to the same length and width as the leaves) between inductors.

In addition, we performed electromagnetic shielding experiments at roughly 1 Hz

frequency. These experiments were performed by replacing the emitting coil and function

generator with a small rare earth magnet that was swung back and forth by hand at roughly 1 Hz

in a regular rhythm. As expected, the receiving coil signal measured by the oscilloscope

comprised a regular rhythm of blips in sync with the magnet motions. We detected no

discernable differences in the measured signal when charged or uncharged leaves were present or

absent. In other words, we detected no appreciable electromagnetic shielding by the charged or

uncharged pair of leaves at this low frequency.

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Table 2: List of shielding experiments performed. All experiments used a 500 mH emitting

inductor placed 3.5 cm away from a 500 mH receiving inductor. Vpp is the measured peak-to-

peak voltage.

Exp.

Number

Input

Frequency

Input

Vpp (V)

Output

Vpp (V)

test

object

sign of

charge

(+,-,0)

Excess

Charge

(Y/N)

1 40kHz 20 1.7 ± 0.1 none 0 N

2 40kHz 20 2.0 ± 0.1 leaves 0 N

3 40kHz 20 1.8 ± 0.1 leaves - N

4 40kHz 20 1.9 ± 0.1 leaves - Y

5 40kHz 20 0.6 ± 0.1 Fe plate 0 N

6 10MHz 20 0.33 none 0 N

7 10MHz 20 0.33 none 0 N

8 10MHz 20 0.33 leaves 0 N

9 10MHz 20 0.33 leaves - N

10 10MHz 20 0.30 Al foil 0 N

11 10MHz 20 0.33 leaves + N

12 46kHz 20 20.4 none 0 N

13 46kHz 20 18.0 Al foil 0 N

14 46kHz 20 20.4 leaves + N

15 46kHz 20 20.4 leaves - N

16 46kHz 20 20.0 leaves 0 N

4. Conclusions and Recommendations

A MED provides a rare example of electrostatic attraction between macroscopic

distributions of like-signed electrostatic charges. The direction of this electrostatic force is

opposite to that predicted by Coulomb’s Law. In this work, we performed electromagnetic

shielding and net charge measurements to better understand a MED.

The metallized dielectric foils in the attractive state of a MED did not provide any

measurable shielding of electromagnetic waves from low frequencies up to and including 10

MHz. 10 MHz corresponds to a wavelength of 30 m. Electromagnetic shielding within the

microwave and infrared regions has been theoretically predicted to occur by scattering off the

electrostatic potential kink at the location of the confined charged layer in each foil.[1] We

recommend that future electromagnetic shielding tests be performed at higher frequencies

corresponding to those within the microwave and infrared regions.

The sensitivity of our net charge measurements was not sufficient to accurately measure

the net charge residing on the charged leaves in the activated attractive state. However,

experiments showed the attractive state between the two charged foils persisted even when the

two leaves had an excess of same-signed charges (Figure 1D and E). Depending on the sign of

the initial charge, the final net charge of the charged leaves in the activated attractive state was

positive in some cases and negative in other cases. We estimate the final surface charge density

of the charged leaves in the activated attractive state to be 10-7 to 10-6 Coul/m2. We recommend

that higher sensitivity experiments be performed to accurately quantify the net charge of the

metallized dielectric foils in this attractive state.

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Acknowledgments

Part of this work was funded through NASA and the New Mexico Space Grant

Consortium.

References

1. T. A. Manz, “The Manz Effect Provides a Table-Top Demonstration of Attraction Between

Electrostatic Charges of the Same Sign,” J. Space Mixing 6 (2016) 1-17.

2. D. Halliday and R. Resnick, Fundamentals of Physics, Third Edition, John Wiley & Sons:

New York (1988) pp. 537-538, 580, 622, 627.

3. E. Nagornyak, H. Yoo, and G. H. Pollack, “Mechanism of attraction between like-charged

particles in aqueous solution,” Soft Matter 5 (2009) 3850-3857.