Change In Electrical Resistance Research Articles

Enhancing wearable humidity sensing with conductive PANi-Coated polyurethane nanofibers

This study presents a flexible nanofibrous humidity sensor for wearable applications and smart textiles. The methodology involved fabricating polyurethane (PU) nanofibers via electrospinning, followed by polyaniline (PANi) coating under varied synthesis conditions. Scanning electron microscopy (SEM) analysis revealed consistent diameter uniformity in the prepared PU nanofibers. Moreover, an increase in average nanofiber diameter (305 to 539 nm) was observed with rising polymer solution concentration (7% to 9%). Fourier-transform infrared spectroscopy (FT-IR) confirmed the physical presence of PANi on PU nanofiber surfaces without inducing structural changes. Additionally, the strength of PU nanofibrous samples, with or without PANi coating, increased proportionally with higher PANi and PU polymer concentrations. Electrical conductivity was measured using a four-point device, and surface resistance was assessed across varying humidity levels to study humidity’s impact on samples. Results exhibited a linear relationship between surface electrical resistance and relative humidity changes. Furthermore, the PU and PU/PANi nanofibers exhibit contact angles of 113° and 133°, respectively. The PANi-coated sample is more hydrophobic compared to the uncoated sample. In conclusion, these findings underscore the potential of the developed sensor as a responsive tool for monitoring humidity fluctuations in diverse applications.

Detecting DC Electrical Resistivity Changes in Seismic Active Areas: State-of-the-Art and Future Directions

In this paper, a critical review of the geoelectrical monitoring activities carried out in seismically active areas is presented and discussed. The electrical resistivity of rocks is one of the geophysical parameters of greatest interest in the study of possible seismic precursors, and it is strongly influenced by the presence of highly fractured zones with high permeability and fluid levels. The analysis in the present study was carried out on results obtained over the last 50 years in seismic zones in China, Japan, the USA and Russia. These past works made it possible to classify the different monitoring strategies, analyze the theoretical models for interpreting possible correlations between anomalies in resistivity signals and local seismicity, and identify the main scientific and technological gaps in the literature. In addition, great attention has been paid to some recent works on the study of the correlations between focal mechanisms and the shapes of anomalous patterns in resistivity time series. Finally, some future scenarios for the development of new activities in this field have been identified.

Effects of thermo-oxidative aging on progressive bending damages and electromechanical behaviors of carbon fiber/epoxy 3D woven composites

The effect of thermo-oxidative aging on mechanical properties is important to designing carbon fiber-reinforced composites serviced in long-term atmospheric environments. Here, we report the progressive bending damage behaviors of carbon fiber/epoxy 3D angle-interlock woven composites (3DAWCs) after thermo-oxidative aging. Three-point bending tests were conducted to characterize bending damage behaviors after different aging days. The electrical resistance change of 3DAWCs was also simultaneously measured with the two-probe method during three-point bending tests. Combining side image and digital image correlation (DIC) technology, we found that the bending strength and modulus deteriorated rapidly during thermo-oxidative aging. The strain distribution and progressive bending damage modes also changed significantly, i.e., a symmetrical strain distribution for the unaged specimens, while the existing interface cracks of the aged specimen changed this symmetry. The electrical resistance method (ERM) effectively identified the early-stage damages, and the first derivative of the rate of resistance change (FDC) revealed differences in the progressive damage modes of aged and unaged specimens.

Void geometry analysis and multifaceted characterisation of cementitious mortar reinforced with short carbon and glass fibres – A comparative study

This paper presents comprehensive experimental and numerical studies on void analysis, durability performance, electrical properties, and microstructural behaviour of fibre-reinforced cementitious composites (FRCC) with varying short carbon and glass fibre volume fractions. Durability and electrical properties are evaluated based on the hydrochloric acid effect, water absorption, drying shrinkage and electrical resistivity changes over time. The incorporation of CF and GF remarkably limits drying shrinkage, primarily attributed to the bridging and bonding effects of fibres within the matrix. The addition of 1.0 % carbon fibre significantly decreases the electrical resistivity and improves acid resistance performance. Furthermore, for the first time, the influence of fibre type and quantity on the formation of elongated and eccentric voids is investigated by using X-ray computed tomography (micro-CT). The results demonstrate that higher porosity leads to lower strength and durability performance, while a greater occurrence of elongated voids contributes to increased length change in shrinkage.

Annealing hardening of the pre-deformed Cu-56at.%Au alloy due to retardation of recrystallization by L1o-type ordering

The evolution of the microstructure, physical and mechanical properties of pre-deformed samples of the non-stoichiometric alloy Cu-56at.%Au in the process of the L1o-type atomic ordering was studied. The duration of annealing at 250 °C ranged from 1 h to 2 months. Changes in microhardness and electrical resistivity at various stages of the disorder→order transition were found out, the microstructure was examined using a transmission electron microscope, XRD-scans and tensile tests were performed. Based on the resistometric results and XRD-analysis, the dependence of the fraction of the ordered phase vs. the annealing time was plotted. Consecutive changes in structural states observed during long-term annealing were considered through the competition between the energy of the elastic stresses, the surface energy and the energy of the dislocation structure. An abnormal increase in the strength properties of the alloy during annealing was found: the yield strength and microhardness of the initially deformed samples significantly increase (at 15 % and 30 %, respectively), at the same time there is a drop in electrical resistivity and an increase in plasticity. An attempt was made to describe the observed phenomena considering mutual effect of ordering and recrystallization. Discovered annealing hardening was explained in terms of the suppression of recrystallization by ordering, which is confirmed by the preservation of a high density of inherited dislocations in an ordered matrix and low plasticity of the annealed samples. The retardation in the recrystallization rate with an increase in the preliminary deformation strain of the alloy was discovered.

Smart ultra-high-performance concrete under cyclic high compressive stress

The self-stress sensing response of smart ultra-high-performance concrete (S-UHPC) under high cyclic compressive stress was investigated at different temperatures between 15 °C and 35 °C as a basic study for understanding the effects of temperature on the self-stress sensing response of S-UHPC. The S-UHPC has maintained the quasi-linear relationship between stress and fractional change in electrical resistivity (FCR) even under cyclic stress. The stress-sensing coefficient (SSC) of S-UHPC almost linearly decreased from 0.2450 %/MPa to 0.1722%/MPa with increasing the temperature from 15 °C to 35 °C. The lower SSC at higher temperature is based on the decreased electrical resistivity (∆ρ) of S-UHPCs owing to more activated ion movements in S-UHPCs.

Predicting soil parameters in Maroua 1st, Cameroon, using correlations of geophysical and geotechnical data

This study aims to predict specific soil parameters based on quantitative and qualitative correlations between electrical and geotechnical data. A total of 21 geotechnical boreholes followed by sampling, 21 light dynamic penetrometer tests, and 76 vertical electrical sounding surveys were carried out in Maroua 1st. The electrical resistivity data of the soil layers were obtained through 1D and 2D inversions of the ERT surveys. The geotechnical data were obtained from field tests and laboratory experiments. The statistical analysis of the entire dataset indicates that most of the samples are clay formations, as demonstrated by the means of variables and low variance coefficients, enabling qualitative identification. The distribution analysis of the parameters confirms the complexity of the physical characteristics of soils and the measurement procedures for each parameter. The Spearman's rank correlation matrix indicates that these observations can be used to propose predictive models for free swelling, allowable stress, natural water content, and electrical resistivity. Correlations between free swelling (εg) and other variables are not significant, as the degree of significance is lower than the fixed limit, except for models εg - W (R2 = 0.94), εg - ρ (Ώ.m) (R2 = 0.803), and εg - σ adm (R2 = 0.757). Grouping variables in multiple linear regression enables the development of a mathematical model. The predicted values of εg from this model demonstrate good agreement with the measured values for a validity domain of 0–16 %. The soil's natural water content has a strong correlation (R2 = 0.80 and rs = – 0.87) with electrical resistivity, meaning that an increase in water content results in a decrease in electrical resistivity. The permissible stress σadm has a strong correlation (R2 = 0.89 and rs = 0.85) with electrical resistivity. This indicates that changes in soil electrical resistivity are associated with soil stiffness.

A new winding homogenization method based on thermal resistance concept

PurposeThe aim of this paper is to provide a simple yet accurate and efficient geometric method for thermal homogenization of impregnated and non-impregnated coil winding technologies based on the concept of thermal resistance.Design/methodology/approachFor regular windings, the periodic microscopic cell in the winding space is identified. Also, for irregular windings, the average microscopic cell of the winding is determined. An approximation is used to calculate the thermal resistance of the winding cell. Based on this approximation, the winding insulation is considered as a circular ring around the wire. Mathematical equations are obtained to calculate the equivalent thermal resistance of the cell. The equivalent thermal conductivity of the winding is calculated using equivalent thermal resistance of the cell. Winding thermal homogenization is completed by determining the equivalent thermal properties of the cell.FindingsThe thermal pattern of different windings is simulated and compared with the results of different homogenization methods. The results show that the proposed method is applicable for a wide range of windings in terms of winding scheme, packing factor and winding insulation. Also, the results show that the proposed method is more accurate than other winding homogenization methods in calculating the equivalent thermal conductivity of the winding.Research limitations/implicationsIn this paper, the change of electrical resistance of the winding with temperature and thermal contact between the sub-components are ignored. Also, liquid insulators, such as oils, and rectangular wires were not investigated. Research in these topics is considered as future work.Originality/valueUnlike other homogenization methods, the proposed method can be applied to non-impregnated and irregular windings. Also, compared to other homogenization methods, the proposed method has a simpler formulation that makes it easier to program and implement. All of these indicate the efficiency of the proposed method in the thermal analysis of the winding.

Electrical Resistivity Behavior of Saline Soil under Low-Temperature Conditions

Freeze-thaw cycling of frozen soils is known to be the cause of various engineering failures of infrastructure in cold regions. Researchers found that electrical resistivity methods outperform traditional ground surveying methods in frozen soils for their greater convenience and cost-effectiveness. However, detailed investigation into the relationship between the electrical resistivity of soil and a variety of soil properties is still needed. In this study, a series of laboratory experiments using the Wenner method were conducted to determine the relationship between soil electrical resistivity and soil geotechnical properties such as initial water content and pore fluid concentration under freeze-thaw conditions. Cylindrical soil samples undergo artificial freeze-thaw cycles to a temperature as low as −70°C, and electrical resistivity and temperature values are recorded simultaneously. Measurement results are summarized for curve fitting, and a statistical model showing relationship between electrical resistivity and temperature during freezing and thawing was given. Above freezing point, the log of electrical resistivity had a linear relationship with temperature. Below freezing point and above −15°C, the log of electrical resistivity had a square root relationship with temperature. Different trends in electrical resistivity change in extremely low-temperature regions (from −15°C to −70°C) are also discussed. In extremely low-temperature regions, the electrical resistivity of frozen soils did not monotonously increase with lower temperature, which may be because of increasing salt concentration in the unfrozen water phase. The findings of this study are expected to bring more insights to frozen soil structure, and assist in geophysical surveying in cold regions and construction methods utilizing ground freezing.

Characterization of a Deglaciated Sediment Chronosequence in the High Arctic Using Near‐Surface Geoelectrical Monitoring Methods

ABSTRACTAccelerated climate warming is causing significant reductions in the volume of Arctic glaciers, such that previously ice‐capped bare ground is uncovered, harboring soil development. Monitoring the thermal and hydrologic characteristics of soils, which strongly affect microbial activity, is important to understand the evolution of emerging terrestrial landscapes. We instrumented two sites on the forefield of a retreating Svalbard glacier, representing sediment ages of approximately 5 and 60 years since exposure. Our instrumentation included an ERT array complemented by adjacent point sensor measurements of subsurface temperature and water content. Sediments were sampled at each location and at two more additional sites (120 and 2000 years old) along a chronosequence aligned with the direction of glacial retreat. Analysis suggests older sediments have a lower bulk density and contain fewer large minerals, which we interpret to be indicative of sediment reworking over time. Two months of monitoring data recorded during summer 2021 indicate that the 60‐year‐old sediments are stratified showing more spatially consistent changes in electrical resistivity, whereas the younger sediments show a more irregular structure, with consequences on heat and moisture conductibility. Furthermore, our sensors reveal that young sediments have a higher moisture content, but a lower moisture content variability.

An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials

Abstract In this study, hybrid functional fillers were used to create an electrical network that is used to develop self-damage sensing ability within conventional cementitious mixtures. This electrical network was used to examine the self-sensing properties of cementitious composites under different loading scenarios such as compression, splitting tensile, and cyclic loading for three ages, those are 7, 14, and 28. With the help of a single type of functional filler or fiber, the self-sensing capabilities of the majority of previous works are demonstrated. This study incorporates two types of functional fillers for sustainability and low cost: micro-scale carbon fibers (CF) and waste iron (Ir) powder in the form of microparticles. The purpose of the current work is to fill up the subject’s gap using two different types of functional fillers as a hybrid form. Three hybrid proportions of a micro-scale CF (vol% of mixture) and waste iron powder (Ir) (wt% of cementitious materials) are utilized. These are (0.33, 15), (0.67, 10), and (1.00, 5), respectively. Unlike carbon-based materials, polyvinyl alcohol is used as a mechanical reinforcing fiber 2% by volume of the cementitious mixture. Additionally, a control combination without any fillers has been created. The electrical resistivity of the fabricated samples was monitored during various loading applications for every second to confirm their self-sensing capabilities. Regarding the fractional change in electrical resistivity, the self-sensing behavior was superior for mixes containing high dosages either of waste iron powder or CF in the same hybrid matrix. Quite the contrary to that, the piezoresistivity was modest in the middle hybrid ratio.

Mechanical Flexibility and Electrical Reliability of ZnO-Al Thin Films on Polymer Substrates Under Different External Deformation

Abstract Aluminum-doped zinc oxide (AZO) films have emerged as promising transparent electrodes for various optoelectronic applications due to their superior transparency, electrical conductivity, and cost-effectiveness compared to indium tin oxide (ITO). Despite their widespread use, investigations into the electromechanical properties of AZO films, especially under various mechanical deformations, remain limited. This study employs RF magnetron sputtering to deposit AZO films on polyethylene naphthalate (PEN) substrates and explores their mechanical behavior through uniaxial tensile fragmentation and bending tests, coupled with in-situ optical microscopy. Changes in electrical resistance of AZO films were monitored in situ during deformation. Fatigue behavior was examined to further understand mechanical failure, and SEM was used for surface characterization. A critical strain of about 3.1 percent was detected during uniaxial tensile testing, marking the onset of cracks in AZO-coated PEN. In contrast to thicker films, thinner films demonstrated improved stretchability beyond the initiation of crack onset strain. Tension and compression bending tests revealed that the material has excellent bendability, as shown by its critical radii of 5.4 mm and 3.9 mm, respectively. The bending reliability of AZO films under compression was found to be superior than that under tension. Bending fatigue experiments demonstrated that AZO films could withstand cyclic stress without experiencing no ticeable cracks after 100 cycles and with very minor resistance change. This study contributes to the creation of more reliable and optimized flexible optoelectronic devices by giving substantial quantitative data on the performance of AZO films when exposed to mechanical stress.

Graphene nanoplatelet/polypropylene pellets in cement-based composites: Mechanical, piezoresistive and microstructural properties

Graphene nanoplatelet–reinforced polypropylene is considered a promising conductive polymer-based additive to provide unique features to cementitious composites. This study comprehensively investigated the collective effects of graphene and polypropylene in the form of graphene nanoplatelet/polypropylene pellets (GrPp). Adding GrPp increased the flexural strength of the cementitious composites due to its high tensile strength. Moreover, the GrPp-enhanced cementitious composites show a high piezoresistive absolute maximum fractional change in electrical resistivity (FCR) of 96.50 %, stress sensitivity of 4.13 %/MPa, and repeatability of 90.81 % with the addition of 2–3.5 wt% GrPp on average. Furthermore, adding GrPp improved the piezoresistive behavior by forming a conductive path and increasing the deformability of the cementitious composites. These findings demonstrate that Gr-reinforced Pp pellets present an economical and efficient way to develop piezoresistive stress sensors for smart cement-based composites.

Comparison between Four-Probe and Two-Probe Electrical Resistivity Measurement to Monitor the Curing and Piezoresistivity Behavior of Smart Cement Paste Modified with Waste Steel Slag and Green Nano-magnetite

Abstract This study aims to examine the compressive strength, electrical resistivity, and piezoresistivity characteristics of ordinary Portland cement (OPC) with a constant water-to-cement ratio (w/c) of 0.38. The optimal value of steel slag (SS) was determined to be 5 % based on the compressive strength of six different mixes of cement paste modified with various SS from 0 % to 30 % weight of cement. Additionally, the investigation will include modified cement samples containing 1 % green synthesized material and commercially available nano-magnetite (NM). Because iron is the primary component of SS and NM, the electrical resistivity, which is the primary criterion for structural health monitoring of cementitious material, can be increased by adding SS and NM. Hence, a comparative analysis was conducted to assess the resistivity of cement paste throughout the early curing period up to 28 days using an alternative current (AC) and embedding wires into the specimen, employing both the two-probe (2P) and four-probe (4P) methodologies. The findings suggest that the 4P method is a more precise approach for determining electrical resistivity than the 2P method, as the wire probe is not considered in the 4P method. Hence, it is imperative to compute the correlation between the 2P and 4P methodologies in order to attain a precise resistivity measurement. The suggested model indicates that the expected 4P resistivity can be measured with high precision, a high coefficient of determination (R2) of .97, and a low root mean square error (RMSE) of 7.33 Ω·m, based on the 2P result. The piezoresistivity results demonstrated that the cement paste modified with green synthesis nano-magnetite (GSNM) had a higher electrical resistivity (ER) change, 10.85 % greater than cement paste only, 57 % higher than cement modified with SS, and 34.2 % higher than cement paste modified with commercial nano-magnetite (CNM) after 28 days of curing. In addition, the compressive strength of cement paste modified with GSNM was higher than that of cement paste, cement paste modified with SS, and cement paste modified with CNM by 15.96 %, 21 %, and 1.7 %, respectively, after 28 days of curing. A Vipulanandan p–q model was used to forecast the electrical resistivity of cement paste versus time at start hydration during 28 days of curing and the change of electrical resistivity versus compressive strength at 3, 7, and 28 days. The Vipulananda p–q model anticipated both electrical resistivity and piezoresistivity behavior well.

Nanoscale morphology, optical dynamics and gas sensor of porous silicon

We investigated the multifaceted gas sensing properties of porous silicon thin films electrodeposited onto (100) oriented P-type silicon wafers substrates. Our investigation delves into morphological, optical properties, and sensing capabilities, aiming to optimize their use as efficient gas sensors. Morphological analysis revealed the development of unique surfaces with distinct characteristics compared to untreated sample, yielding substantially rougher yet flat surfaces, corroborated by Minkowski Functionals analysis. Fractal mathematics exploration emphasized that despite increased roughness, HF/ethanol-treated surfaces exhibit flatter attributes compared to untreated Si sample. Optical approaches established a correlation between increased porosity and elevated localized states and defects, influencing the Urbach energy value. This contributed to a reduction in steepness values, attributed to heightened dislocations and structural disturbances, while the transconductance parameter decreases. Simultaneously, porosity enhances the strength of electron‒phonon interaction. The porous silicon thin films were further tested as effective gas sensors for CO2 and O2 vapors at room temperature, displaying notable changes in electrical resistance with varying concentrations. These findings bring a comprehensive exploration of some important characteristics of porous silicon surfaces and established their potential for advanced industrial applications.

Urinary cancer detection by the target urine volatile organic compounds biosensor platform

Volatile organic compounds (VOCs) have grown due to their crucial role in transitioning from invasive to noninvasive cancer diagnostic methods. This study aimed to assess the feasibility of the metal oxide biosensor platform using urine VOCs for detecting genitourinary cancers. Five different commercially available semiconductor sensors were chosen to detect specific VOCs (methane, iso-butane, hydrogen, ethanol, hydrogen sulfide, ammonia, toluene, butane, propane, trimethylamine, and methyl-mercaptan). Changes in electrical resistance due to temperature variations from the voltage heater were examined to characterize VOC metabolism. Logistic regression and ROC analysis were employed to evaluate potential urine VOCs for genitourinary cancer determination. This study involved 64 participants which were categorized into a cancer and a non-cancer group. The genitourinary cancer (confirmed by tissue pathology) comprised 32 patients, including renal cell carcinoma (3.1%), transitional cell carcinoma (46.9%), and prostate cancer (50%). The non-cancer comprised 32 patients, with 9 healthy subjects and 23 individuals with other genitourinary diseases. Results indicated that VOC sensors for methane, iso-butane, hydrogen, and ethanol, at a voltage heater of 2000 mV, demonstrated a significant predictive capability for genitourinary cancer with P = 0.013. The ROC of these biomarkers also indicated statistical significance in predicting the occurrence of the disease (P < 0.05). This report suggested that methane, iso-butane, hydrogen, and ethanol VOCs exhibited potential for diagnosing genitourinary cancer. Developing gas metal oxide sensors tailored to these compounds, and monitoring changes in electrical resistance, could serve as an innovative tool for identifying this specific type of cancer.

Additive fabrication of pressure sensitive material for flexible pressure sensor and its characteristics

The increasing interest in wearable devices and healthcare has sparked significant advancements in the development of flexible sensors for various applications. In this study, we present the fabrication and characterization of a flexible pressure sensor utilizing a three-dimensional structure of pressure sensitive material, fabricated through a layer-by-layer process. The aim of this research is to investigate the electrical response characteristics of the sensor based on the number of layers in the pressure sensitive material, both under static and dynamic pressure conditions. The pressure sensitive material, consisting of multi-walled carbon nanotubes (MWCNTs) dispersed in polydimethylsiloxane (PDMS), exhibits positive piezo-resistive properties. The flexible pressure sensor was fabricated using direct ink writing (DIW) technology, which enables precise control over the arrangement of the material. We explored the influence of layer configurations on the sensor's initial resistance and electrical resistance changes by varying the number of layers. Our experiments demonstrated a clear trend, indicating that as the number of layers increased, both the initial resistance and electrical resistance change decreased. This behavior can be attributed to the enhanced connectivity among carbon nanotubes within the material, resulting in reduced overall resistance. In addition to static pressure testing, we conducted dynamic pressure experiments to assess the sensor's response under rapidly changing pressure conditions. Our findings suggest that by manipulating the number of layers in the pressure-sensitive material, the sensor's sensitivity and detection range can be tailored to suit specific applications. This approach offers a flexible and unified method for fabricating sensors with diverse response behaviors within a single manufacturing process.

Strain Analysis on Cast-In-Place Balanced Cantilever Prestressed Concrete Bridges During Construction

This article shows the strain analysis on two cantilever cast-in-place prestressed concrete bridges during construction. Strain gauges, measuring strain based on the change in electrical resistance, were installed on both structures in order to obtain strain results during and after construction. Nonlinear numerical models were made to simulate the realistic behaviour of the structure and show the effect of creep and shrinkage during the construction phases. The numerical model taking into account creep and shrinkage is validated and shows good overlap with the measured results. Relative compressive stresses as well as the necessary precamber are shown. The effects of creep and shrinkage are analysed. Finally, the data can be used to analyse and compare other similar bridges and validate different numerical models. A recommendation for the design of future prestressed concrete balanced cantilever bridges is given.

Synthesis and Characteristic Valuation of a Thermoplastic Polyurethane Electrode Binder for In-Mold Coating.

A polyurethane series (PHEI-PU) was prepared via a one-shot bulk polymerization method using hexamethylene diisocyanate (HDI), polycarbonate diol (PCD), and isosorbide derivatives (ISBD) as chain extenders. The mechanical properties were evaluated using a universal testing machine (UTM), and the thermal properties were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PHEI-PU series exhibited excellent mechanical properties with an average tensile strength of 44.71 MPa and an elongation at break of 190%. To verify the applicability of different proportions of PU as an electrode binder, PU and Ag flakes were mixed (30/70 wt%) and coated on PCT substrates, the electrodes were evaluated by four-point probe before and after 50% elongation, and the dispersion was evaluated by scanning electron microscopy (SEM). The electrical resistance change rate of PHEI-PU series was less than 20%, and a coating layer with well-dispersed silver flakes was confirmed even after stretching. Therefore, it exhibited excellent physical properties, heat resistance, and electrical resistance change rate, confirming its applicability as an electrode binder for in-mold coating.

Origin of the extreme and anisotropic magnetoresistance in the Weyl semimetal NbP

The fascination with semimetals, especially Dirac and Weyl semimetals, is given by their surprisingly strong response to magnetic fields. In particular, the extremely large magnetoresistance (XMR), i.e., the change in electrical resistivity as a function of the applied magnetic field, has attracted interest because of its deviation by several orders of magnitude from the behavior of normal metals, and its potential for technological applications. To date, it is unclear if the XMR in topological semimetals is inherently correlated to the very high electron mobility and electron-hole compensation, or to other exotic mechanisms. Here, we show that the relativistic and topological nature of charge carriers of the Weyl semimetal niobium phosphide (NbP) are only indirect causes of the XMR. Instead, the XMR can be explained by the very long mean free path le(4K)≈8µm in combination with the small cyclotron orbits emerging in the presence of a magnetic field rc(9T)≈20 nm of the NbP's Weyl electrons. More precisely we find MR=cle/rc, where c is a parameter independent of temperature and angle between the magnetic field and the crystal. To demonstrate, we use temperature and angle-dependent magnetoresistance measurements, and extract the mean free path and cyclotron radius from an analysis of the Shubnikov–de Haas oscillation. Published by the American Physical Society 2024