Electrical current voltage

Scientists measure many different quantities—length, volume, mass (weight), electric current, voltage, resistance, temperature, pressure, force, magnetic field intensity, radioactivity, and many others. The metric system and its recent extension, Systeme International d Unites (SI), were devised to make measurements and calculations as simple as possible. In this section, length, area, volume, and mass will be introduced. Temperature will be introduced in Sec. 2.7 and used extensively in Chap. 12. The quantities to be discussed here are presented in Table 2-1. Their units, abbreviations of the quantities and units, and the legal standards for the quantities are also included. 

U.S. Patents using electrical currents/voltages for soil remediation have been issued to Probstein et al. [65] and Acar and Gale [64]. 

Currently, various technologies are used to increase the permeability of macromolecules by exploring iontophoresis, electroporation, ultrasound, and micro-poration using electrical current/voltage, radio frequency, and microneedles to open the skin. Although mechanical abrasion and chemical enhancers may increase drag permeation, their effects on the skin s inherent rate-controlling properties are difficult to control and they may irritate the skin [85]. 

The relationship among electric current, voltage, and time during electrical dressing is shovm in Figure 6.6. When predressing starts (point 1),... 

Frequency is measured in hertz, cycles per second. This is the number of times each second that the electric current/ voltage changes direction. Some common frequency values associated with electrical systems are ... 

Woermann, D., Analysis of non-ohmic electrical current-voltage characteristic of membranes carrying a single track-etched conical pore. Nuclear Instruments Methods in Physics Research, Section B Beam Interactions with Materials and Atoms 2002,194, 458-462. 

Electric shock is the sudden pain or convulsion which results from the passage of an electric current through the body. Minor electrical shocks may cause mishaps due to involuntary reactions. Major electrical shocks may cause death due to burns or paralysis of the heart or lungs. An electric shock results from the passage of direct or alternating electrical current through the body or a body part. Electrical current/voltage in a system is a basic hazard source for many types of electrical related hazards, all of which should be identified in a system safety HA. 

The graph of Figure 6.8 illustrates the effect of increasing voltage on the electric current between two electrodes immersed in a gas. The circuit is completed by an external resistance, used to limit the current flow. As shown in Figure 6.8, the discharge can be considered in regions, which are described below. 

Under suitable conditions of pressure and other factors, application of a suitable voltage between electrodes immersed in a gas causes a discharge of electric current through the gas. Different... 

The electrolyte thus formed can conduct electric current by the movement of ions under the influence of an electric field. A cell using an electrolyte as a conductor and a positive and a negative electrode is called an electrolysis cell. If a direct-current voltage is appHed to a cell having inert electrode material such as platinum, the hydrogen ions (cations) migrate to the cathode where they first accept an electron and then form molecular hydrogen. The ions... 

The electrical-resistance method involves passing an electric current through the structure and exploring the surface with voltage probes. Flaws, cracks, or inclusions will cause a disturbance in the voltage gradient on the surface. Railroads have used this method for many years to locate transverse cracks in rails. 

An electric current, rather than voltage, through a human body may cause shock and can damage vital organs of the body as follows ... 

This handbook deals only with systems involving metallic materials and electrolytes. Both partners to the reaction are conductors. In corrosion reactions a partial electrochemical step occurs that is influenced by electrical variables. These include the electric current I flowing through the metal/electrolyte phase boundary, and the potential difference A( = 0, - arising at the interface. and represent the electric potentials of the partners to the reaction immediately at the interface. The potential difference A0 is not directly measurable. Therefore, instead the voltage U of the cell Me /metal/electrolyte/reference electrode/Me is measured as the conventional electrode potential of the metal. The connection to the voltmeter is made of the same conductor metal Me. The potential difference - 0 is negligibly small then since A0g = 0b - 0ei ... 

Practical measurements providing data on corrosion risk or cathodic protection are predominantly electrical in nature. In principle they concern the determination of the three principal parameters of electrical technology voltage, current, and resistance. Also the measurement of the potential of metals in soil or in electrolytes is a high-resistance measurement of the voltage between the object and reference electrode and thus does not draw any current (see Table 3-1). 

Arc Resistance ASTM D495. When an electric current is allowed to travel across the surface of an insulator the surface will become damaged over time and become more conductive. The arc resistance is a measure of the time (in seconds) required to make an insulating surface conductive under a high-voltage, low-current arc. 

---