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How Do Air and Magnetic Hydraulic Circuit Breakers work?

Circuit breakers have replaced fuses in most electric circuits. As these are easy to select, install, and maintain, circuit breakers are more commonly employed as protection against over-current and shorts. For different applications, there are various types of circuit breakers available in the market. We will discuss two of them.

Air Circuit Breakers

Air circuit breakers use air as the medium for extinguishing the arc formed when the breaker trips. The air is usually kept in compressed form inside a cylinder. As the breaker trips and the contacts separate, the compressed air, blown through specially designed nozzles, drives the arc into a special arc chute.

Electric circuits working in the Low Voltage (LV) range use air circuit breakers extensively and they can interrupt currents of several thousand amperes. Air circuit breakers work with an inherent current sensing mechanism, which is similar to the thermo-magnetic release.

To weaken the arc, the air circuit breaker uses a component called the arc chute. This has a number of splitters to split the arc into several sections—increasing the length of the arc—thereby quenching it. The arc chute is usually made of composite refractory material, and pressurized air drives the arc, formed during the separation of the fixed and moving contacts, into this arc chute.

The industry uses air circuit breakers widely for protection of facilities and transmission lines, and these breakers are available in both three- and four-pole versions. Air circuit breakers protect electric equipment such as motors and transformers as well. Ships and mines also use air circuit breakers for protection.

Magnetic Hydraulic Circuit Breakers

Magnetic Hydraulic Circuit Breakers use the principle of magnetic effects of current to operate. Although similar in operation to the standard magnetic circuit breaker, the magnetic hydraulic circuit breaker differs as the latter has a hydraulic time delay mechanism.

The delay comes from forcing the core to move through a cylinder filled with silicone fluid. During over-current, the magnetic field it creates pulls the core into the cylinder. As the core has to pass through the silicone fluid in the cylinder, it slows down, introducing the time delay.

Therefore, after a momentary over-current has passed, the core can return to normal, without the circuit breaker tripping. With a persistent over-current, the core ultimately reaches the coil.

As the core enters the coil, it changes the reluctance of the magnetic circuit. This increases the resultant flux, which ultimately attracts the armature causing the protecting device to trip and thereby, separate the contacts.

With the contacts separating, the over-current reduces to zero. This kills the magnetic field, releasing the core to return to its original position.

This feature is a great advantage of the magnetic hydraulic circuit breakers—they automatically reset immediately after tripping. Other circuit breakers with thermal over-current elements require a cooling period before they can be reset.

Independent of the ambient operating temperature, magnetic hydraulic circuit breakers offer accurate and reliable over-current protection. The industry uses them extensively as they are relatively inexpensive and available for both AC and DC applications.

How Long Does it take for a Circuit Breaker to Operate?

Electrical power systems all over the world use circuit breakers as important and critical components. As they play a key role, engineers periodically test circuit breakers. One of the most important test methods is the timing test, which measures the mechanical operating time of the breaker’s contacts. A timing test averts damage to a circuit breaker, as the incorrect operation of a circuit breaker prevents fatal consequences on connected equipment and substation personnel.

Various measuring devices have evolved for measuring the operation times of a breaker. For instance, although are no longer in use, first-generation devices used the oscillographic mode of recording curves. The present methods of testing, the second generation, are based on digital timers converting pulses to time. The latest concept for testing circuit breakers is through the analysis of signals from mechanical vibration.

Circuit Breaker Operation Times

The technically operational quality of a three-phase circuit breaker is an important parameter of its operation times—characterizing the process of opening and closing of its contacts. The international standards of the International Electrotechnical Commission, the IEC 56.3.105, define these time parameters. The standard quantitatively describes the switching on and off times of the process as:

Time discrepancy between contacts — the diverging interval characterizing the disconnection or connection of the breaker contacts during non-simultaneous switching.

Closing time — the interval from the time of energizing the closing circuit (the circuit breaker being in the open position), to the moment the contacts strike the poles.

Opening time of the breaker — the interval from the time of energizing the opening release (the circuit breaker being in the closed position), to the moment the contacts separate at all the poles.

Worth noting is the time discrepancy between the contacts of the breaker. This should be within specified tolerance limits—usually 5 ms. This is important, as the time difference in closing or opening of all contacts may cause huge voltage spikes with a potential to damage the network and its equipment.

Digital Timer Meter

Digital timer meters are typically built with interconnected functional blocks such as input circuits, the micro-controller, a display, and a keyboard. The micro-controller is the central unit of the meter, while the input circuit eliminates disturbances and protects the unit.

The input circuit usually includes a converter with an output voltage of about 50 V. An opto-isolator ensures the optical isolation between the parts of the device directly connected to the breaker under test, and the other circuits of the meter. This protects components and digital circuits to ensure standardization of the signal for further digital processing.

Principle of Operation

The measuring process employs a principle known as the time-pulse method. This allows counting of pulses of a regular frequency in time intervals. The software in the micro-controller allows counting the pulses initiated by an external signal obtained from the breaker’s drive system.

A signal corresponding to the opening or closing of each contact of the breaker closes the time gates. As soon as the signals for the contact closure appear, the micro-controller copies the contents of the counter into its memory. The number of pulses the micro-controller counts is proportional to the interval elapsed from the moment of triggering to the moment of closing.

Metal Bellows in Engineering Applications

Metal bellows are versatile and a key enabling technology for a wide range of engineering applications. They play an essential role in controlling motion, vacuum, and pressure. Numerous industry sectors use metal bellows in a broad array of machine assemblies and components.

Being flexible, spring-like, and precision-engineered components, metal bellows are typically custom-designed, performing a variety of engineering functions. Metal bellows can convert temperature, mechanical, and pressure changes to linear or rotational motion. Flexible electronic applications can also use them.

Although the metal bellow is only a small part within the overall machine assembly, the role it plays is a critical one in the overall functionality of the system. While elegantly addressing a number of engineering challenges, a range of applications uses the bellow. These include—mechanical test stands, agriculture, solar power, semiconductor, ultra-high vacuum, cryogenic, military and defense, oil and gas service, aerospace, instrumentation, and industrial automation.

As part of the larger machine component or assembly, bellows generate a specifically defined dynamic response. In some cases, this provides a more precise, more reliable, and less expensive alternative to a more complex engineering solution.

Typical Applications

With advanced manufacturing techniques, designers can engineer metal bellows with precision and manufacture them with extremely small dimension. Several engineering applications benefit from using metal bellows and different engineering scenarios demonstrate their broad functionality.

Sensitive military and aerospace applications use the highly reliable metal bellows as mechanical backups for their mission-critical electronic systems.

Form and Function

A metal bellow has the physical form of a spring-like accordion, and is flexible and lightweight. Manufacturers fabricate bellows as a part of a leak-tight sealed assembly, having appropriate ends for allowing connections within the equipment. In both vacuum and pressure applications, the bellows appears as a ribbed or corrugated tubing.

The bellows can function like a spring for many engineering applications. However, when filled with a pressurized gas or liquid, or in conditions of vacuum, the bellows displays extreme sensitivity to various forces such as temperature and pressure changes affecting the hydraulic gas or fluid sealed within or outside the bellows. Knowing the coefficient of expansion of the gas or fluid, the designer can fashion the bellows to provide a dynamic and predictable mechanical response against these forces.

Mechanical Actuation

Sealed metal bellows, filled with a known silicone-based fluid, will extend or compress with temperature changes. This happens as the fluid inside experiences volume changes, in response to falling or rising temperature. The change in fluid volume translates into a linear movement of the bellows, producing a predictable response. Used within a machine assembly, the bellows provides precision positioning.

The advantage with thin-walled bellows is they remain flexible even under cryogenic conditions, suffering no compromise in their stroke. Since bellows retain their integrity and do not crack even at such low temperatures, they are very reliable for coupling, offset, rotation, extension, and compression capabilities. For instance, they are used reliably for pumping liquid nitrogen, liquid helium, and liquid oxygen in space valve applications.

The thermal expansion of the concealed fluid allows metal bellows to be used as indicators of temperature and pressure. Missile technology and navigation make use of metal bellows where low-temperature operations are critical. Astronomy applications use bellows for positioning mirrors precisely.

How Does Ladder Logic Work?

Over the last 30 years, there has been a significant evolvement of ladder logic for industrial controllers. It now supports advanced functionality that includes data acquisition, networking, data manipulation, motion control, and process control. Designers starting a new control system are faced with many basic functions this tried-and-trusted language needs to perform, and it does so, almost effortlessly.

Object Detection

Detecting the presence of an object is one of the most pervasive functions a control system is asked to perform. Whether it involves detecting an object passing by on a conveyor, the closing of a gate, or locating a machine part as it revolves, object detection is a staple function in the automation industry. Objects can be sensed in myriad ways, and these include mechanical, inductive, capacitive, optical, and ultrasonic techniques and devices to detect proximity or nearness.

Limit Switches

The limit switch is a most basic sensor, mostly an electromechanical device detecting the absence or the presence of an object. As the actuator of the switch touches the sensed object, it operates a set of contacts. Depending on the actuator style, the specific means of contact may vary from plungers to wands, springs, levers, and rollers. However, the moving parts are prone to damage and wear, and it may not always be possible or desirable to make physical contact with the object to be sensed.

Inductive Proximity Switches

Non-contact sensing technology uses inductive proximity switches to detect the absence or presence of metallic objects without actually making contact with it. These are the most common and inexpensive devices. Inside the proximity switch is an oscillator driven coil. The magnetic field created by the oscillator appears at the active face of the switch. As soon as a metal target approaches this area, the electromagnetic field reduces, and this turns the switch on or off.

Capacitive Sensors

For objects that have a dielectric constant different from air, detecting them is easy with a capacitive sensor. Unlike the inductive proximity sensors that sense only metal objects, capacitive sensors can detect plastic, liquids, and wood. Although their method of operation is similar to that of the inductive proximity sensors, capacitive sensors detect objects based on an electrostatic field rather than an electromagnetic field.

Ultrasonic Proximity Sensors

These sensors measure the time of flight of a burst of sound impulse from the source until detecting the echo signal returned by a reflection from the detected object. Almost all materials reflect ultrasonic sound, which remains unaffected by color, transparency, or polish of the object.

Photoelectric Sensor

These sensors use a light beam as the detecting medium. Most popular photoelectric sensors are the diffuse, reflective, and through-beam types. The sensing distance depends on the type of light used—laser, LED, infrared, or visible.

Diffuse Sensors

Diffuse sensors contain both the receiver and emitter in the same unit. The optical beams may be either slightly diverging, or parallel. When an object appears in the luminous beam, it causes diffused reflection. The receiver detects the reflections from the object.

The ladder logic represents the contacts of the sensor and the PLC CPU assigns it a memory location. The CPU represents them in the Normally Open or Normally Closed in the ladder logic.

PiFM: A Pirate Radio with the Raspberry Pi

The popular single board computer, the Raspberry Pi (RBPi), can work as a radio transmitter as well. Using a simple hack, you can turn your RBPi into a powerful FM transmitter with adequate range to cover a bike parade, high school ball game, silent disco, DIY drive-in movie, or even your entire home. However, the broadcast frequency covered by the RBPi is rather large—one to 250 MHz, and there is a possibility this will interfere with government bands. Therefore, it is advisable to limit the transmissions to the standard FM band of 87.5 to 107.9 MHz.

You do not need much to make the RBPi start transmitting. The RBPi board itself, a power source, and the SD card with the OS is all that is necessary. The only accessory required is a piece of wire, which acts as the antenna. The entire project runs on the software PiFM.

Oscar Weigl and Oliver Matios developed PiFM originally, and Ryan Grassel revised it. This project uses the PirateRadio.py script, which enables playback without accessing the command line, while handling most common music file formats automatically. Wynter Woods, a MAKE labs engineering intern, wrote the script.

Oscar and Oliver had hacked the original PiFM code over a few hours. To output FM radio energy, their code used the hardware on the RBPi that actually generates spread-spectrum clock signals on the GPIO pins. Therefore, to turn the RBPi into a really powerful FM transmitter, all that was necessary was to add a wire length acting like an antenna to one of the GPIO pins. The original code used the GPIO pin 4 with a wire of length about 20 cm attached to it. For transmission, Oscar and Oliver had chosen the frequency of 100.0 MHz.

When Sam Freeman and Wynter Woods tested the present project, they found the FM signal only deteriorated once it had to pass through several conference rooms with heavy walls. The signal was able to cover 50 m easily, and objects such as heavy metal cabinets could stop it. They found the sound quality acceptable, although it has some clicks that came from the CPU switching to tasks other than playing music. For the technically minded, a kernel mode driver uses the DMA controller for preventing the RBPi CPU from being loaded, and thereby plays smooth music.

The Python script calls a C program that maps the peripheral bus of the physical memory into virtual address space. After this, it enables the clock generator module and sets points its output to GPIO4. Note that you will not be able to use any other GPIO pin at this time. It also sets the frequency of transmission to 100.0 MHz, which acts as the carrier. If you receive this on a radio, the radio will stop the background noise and become silent.

The carrier is modulated by the audio produced by adjusting the frequency using the fractional divider between 100.025 and 99.075 MHz. The fractional divider can produce audio with only 6-bit resolution. As the RBPi is very fast, it can use 128 subsamples on every real audio sample to produce 9.5-bit audio. The subsample algorithm now gives full 16-bit quality sound with FM pre-emphasis.

A Drone-Disabler with the Raspberry Pi

Drones or quad-copters are now affordable, and it is possible to record unique perspectives using their high quality video transmissions. The FAA calls them the unmanned aircraft systems, and these have started posing new challenges to security, safety, and privacy. Experts have started cautioning pilots to consider the implications of the increase in drone usage. Apart from constant surveillance concerns, it is possible for hackers using roving drones to collect location information from mobile devices.

The above has given rise to a cottage industry for anti-drone technology. You can find these devices in a variety of sizes, from handheld tools to plane-mounted types. It is possible to build one using the popular single board computer, the Raspberry Pi (RBPi). However, this rig will work against only Wi-Fi controlled network-based quad-copters. Please be careful to use this technique only on networks and devices that you own, or have permission to experiment, as otherwise, it may be considered illegal.

Many quad-copters use Wi-Fi as the key interface for communication between its controller and the tablet displaying mapping and telemetry data. Others use Wi-Fi as the sole means of control, and existing network-based attacks can be used against these devices. Since modern drones can be treated as flying computers, the attacks developed for use against traditional computer systems are also effective against drones. To illustrate the project, the AR.Drone 2.0 is selected, as it is a low-cost drone with impressive features and sensors.

Using a smartphone, a user can connect to the AR.Drone 2.0 via an access point named ardrone2. It is easy to connect, as the access point is open by default, does not require authentication, and there is no encryption involved. As soon as the user connects to the device through the access point, launching an app allows control of the drone. Although convenient for the user, the process also makes it easy for others to take control of the drone.

Therefore, using a laptop computer or on an RBPi along with a USB Wi-Fi card and a new antenna, it is possible to attack and take over the controls of the drone. For instance, if a friend is flying the AR.Drone 2.0 using the app, the access point will show up in your available wireless network.

The RBPi uses two executable scripts, one to connect to the access point, and the other to disable the drone. Use the first to connect to the network and start up your favorite terminal application. Usually, the default gateway address for this network is 192.168.1.1. As the access point is wide open on the drone system, it is possible to telnet to this address easily. Once you have access, you can proceed to explore the system, or to shut if off entirely.

This project needs a good antenna for effective connectivity. Connecting a good antenna to the wireless device can also extend its range. If you want a directional antenna, it is advisable to go for a cantenna, and you can easily make one from an available empty beer can. The cantenna will allow you control the selected drone without affecting any other device nearby.

The Next Generation Wireless Audio

We have been seeing wirelessly connected speakers for quite some time now, mainly using the Bluetooth technology. Although convenient, Bluetooth technology has its limitations because of bandwidth and range. The first to overcome this was Sonos who introduced Wi-Fi based wireless speaker system with their SonosNet mesh-networking technology. Several others followed, such as DTS’s Play-Fi, DLNA or Digital Living Network Alliance, and Apple AirPlay among the leading few. The most recent is the Google Cast protocols to allow sending audio over Wi-Fi in different ways. However, the lack of standardization gives consumers several choices.

Next few years will see key players taking the center stage in wireless audio. Among these will be Sony, Harman, Bose, Sonos, Google, and Amazon, among a few others. Amazon has already made its mark with the highly successful Amazon Echo, a voice-enabled speaker and virtual assistant. It is rivaled by the Google Home device, which works like a smart-home control center and a virtual assistance as well. By pivoting round the voice-enabled interactive products, the market is offering users a choice of looking away from the phone screens for some time of the day.

The key challenge for voice-enabled systems will be the design of the microphone-array, as these will be crucial to allow the device to accurately interpret the users voices both in the near- as well as far-field scenarios. Amazon’s product has an excellent voice-listening capability.

On the other end of the spectrum of products are the wireless headsets, headphones, and earbuds. Although most use Bluetooth and BLE or Bluetooth Low Energy, some will be using Wi-Fi in the near future. For instance, Apple has introduced its wireless AirPods. Therefore, such wireless hearables will be coming up strongly. These products will be governed by the requirements of super-low current consumption and long battery life.

For OEMs introducing multi-channel and multi-room audio systems such as 5.1, 7.1 and others, the key challenge will be delivering an audio stream synchronized to all the devices on the network. Systems will need time-stamped algorithms for all packets entering or leaving for ensuring perfect synchronizing of the audio output to the speakers. Different nodes on the network will have varying latency, and the OEMs will need to address these, to keep the system in synch for both over the air as well as through the system channels.

There is extensive fragmentation among Bluetooth audio standards. For instance, there are Miracast, DLNA, DTS Play-Fi, SonosNet, Spotify Connect, Google Cast, Apple’s AirPlay, A2DP, and others. All have their own differentiating features, with business leaders pushing their own ecosystems for their business and technological reasons. However, these remain popular as they cater to different segments of users.

Although Bluetooth is very popular, easy to use, low power, low-cost, and a wide range of devices has the technology built-in already, it is limited by range and the inability to handle more than one device at a time. AirPlay works only with Apple hardware and software. Google Cast, Play-Fi, and Spotify Connect work with Wi-Fi, and these enable streaming audio over longer distances and to multiple speakers at the same time.

Raspberry Pi Goes Binocular

This project uses the popular single board computer, the Raspberry Pi (RBPi) and a spare pair of binoculars to view and take pictures. The LCD on the RBPi is touch enabled to make it easy to capture the images.

To start with, you will need the appropriate Operating System for the RBPi. Download the Wheezy Raspbian OS from the Adafruit site, which will make it easy to interface the 2.8” TFT LCD with a capacitive touchscreen from Adafruit. Once download is complete, unzip the image and install it on the SD card. For the RBPi, you will need the Pi camera with its cable.

Make a suitable arrangement to mount the RBPi and LCD securely on the binoculars and place the camera on one of the eyepieces. This will tell you if the default cable that came with the camera is enough for the purpose or you need to order a longer one. A Wi-Fi dongle (USB type) makes the entire arrangement suitable for transmitting images over the net. In the absence of a Wi-Fi dongle, connect the RBPi to your network using an Ethernet cable.

To configure the RBPi, initially you may have to start with the Raspberry Pi Software Configuration Tool, by logging in and running the command “sudo raspi-config.” This will allow you to set the language, time zone, and keyboard layout according to preference. Additionally, you will also be able to enable the camera, set up the IP address, and the Wi-Fi credentials, which the RBPi will use to communicate.

You can mount the RBPi over the camera in a number of ways, depending on the material available. It is possible to do this with stiff cardboard, thin plywood, and tape. Measure the binoculars and the RBPi to make a suitable cutout in the cardboard. This may require using jigsaw, drill, or laser cutters. If you have access to a 3-D printer, take more accurate measurements, make a suitable image using engineering software, and print a template. Whatever the method of mounting, make sure the RBPi is secure and does not fall over.

Power up the RBPi and the camera and you should be able to see the image on the LCD screen. Place the camera on one of the eyepieces so that light passes through the binoculars and falls on the camera lens. Adjust the position of the camera until you see a well-defined circle on the screen. Now secure the camera to the eyepiece with tape.

For transportability, use a rechargeable battery pack to power the RBPi. For instance, a 2300 mAh battery pack will allow around two hours of operation. To prevent corruption of the SD card, program the RBPi for safe shutdown well before the two hours is over. If the battery pack is also mounted on the binoculars, the total weight may increase, making it difficult to hold and adjust. It might help to have the battery pack on a long enough USB cable, to allow the pack to be kept in the pocket.

It is necessary to connect the RBPi to the Internet if you want the images properly time-stamped. As the RBPi does not have an internal clock, it has to synchronize the date and time with the Internet connection.

What Active Safety Systems do Cars Use?

As cars move towards independence from drivers, and become more self-reliant, they are also becoming smarter and safer. Manufacturers are using newer systems every year for the assistance of drivers with the systems increasingly employing advanced technology and data processing. Among such advanced technology range from automatic high-bean control to pre-collision braking systems, and these are now becoming the norm in practically all kinds of cars.At present, the active safety systems manufacturers use in cars are mainly in the form of three major sensors – LIDAR, radar, and cameras. While assisting drivers in cars, these sensors offer benefits in different ways. Manufacturers also combine these with other sensors for achieving better solutions.

Light Detection and Ranging – LIDAR

This technology relies on lasers to measure distance. When used for automotive applications, the LIDAR system uses infrared lasers firing hundreds of pulses every second. The system measures the time of flight for the reflected light to return to the sensor. The distance to the object is then half of the time of flight times the speed of light.

LIDAR systems are in use by major car manufacturers, including Toyota, Volvo, Continental, and Infinity. These and other manufacturers often combine LIDAR sensors with other technologies such as radar and cameras to provide additional information. For instance, the MFL system from Continental combines LIDAR with a multifunctional camera that Toyota uses for providing automatic high-beam control, lane departure alert and a pre-collision system.

Radio Detection and Ranging – RADAR

One of the oldest and predominant sensor technologies, radar is used for advanced driver safety systems in automotive applications. These safety systems measure the time of flight, frequency shift, and the amplitude of the return signal for determining the relevant information. Automotive applications use radar systems for monitoring blind spots and provide warning for forward collision.

Similar to the LIDAR sensors, other technologies are used in conjunction with radar to obtain better information. By combining a camera and radar into a single package system, mounted in front of the rearview mirror inside the car, it offers multiple functionality such as traffic sign recognition, headlight control, object detection, pedestrian detection, full autonomous braking, pre-crash collision mitigation, forward collision warning, headway alert, lane departure warning/lane keeping, and full-speed adaptive cruise control.

Daylight and Night Vision Cameras

Driver assistance systems majorly rely on cameras, either on their own or by augmenting other systems using computer vision algorithms. Powerful processors extract valuable data using sophisticated image processing in real time. Some cars contain multiple cameras for providing different forms of data to the driver.

Cameras are also useful in assisting the driver to remain attentive when driving. For instance, the Driver Status Monitor from DENSO uses a system of cameras for detecting the driver’s head position, drowsiness level, long-duration eye closure, and the face angle to determine if the driver is distracted of drowsy. IR LEDs provide illumination for nighttime detection. The system then produces a suitable warning for the driver.

In the Future

A decade ago, such systems would be part of science fiction and even five years earlier, these safety systems were part only of luxury vehicles. However, these are commonplace now. Maybe, within the next five to ten years, self-driving cars will be the norm and people will take these and other safety systems for granted.

Can Electrocution Really Kill You?

Although cartoons tend to show a person being fried due to electrocution as the body flashes like fireworks with the bones visible to everyone, in reality, things do not work that way. Electricity does not actually fry you – unless you are struck by a thunderbolt. However, only a frighteningly miniscule amount of electricity is enough to snuff out your life.

At the beginning, it is necessary to get some facts clear. Some major units used by electrical engineers are – volts, amperes, watts, and ohms. Volts describe the difference in potential across two points, while amperes describe the amount of current flowing between the two points. Watts is a measure of the power flow between two points, and is the product of volts and amperes related to the two points. Ohm measures the resistance of a substance to the flow of current through it.

Plumbing offers a suitable analogy. Volts can be equated to the water pressure between the two ends of a pipe. Current is the same as the flow rate, while resistance is similar to the inner diameter of the pipe. As you increase the volts or the pressure, current, or water flow increases, assuming the diameter or resistance of the pipe has remained the same.

Scientists have conducted experiments on healthy humans to find an answer to “How much electricity is needed to kill a human?” The surprise answer is, only seven milli-amperes, for three seconds. Heart is an electrical pump and electricity reaching the heart interrupts its rhythm. The human heart goes arrhythmic and stops working when a current of seven milli-amperes passes through it continuously for three seconds. After that, the other parts of the body begin to shut down as well. Skin-penetrating Tasers do not kill, as the electric pulses they generate are of much shorter duration than that from three seconds.

However, our bodies have their own defenses against electric shock and that is why millions of people do not drop dead every minute with ultra-tiny shocks from the different electrical and electronic gadgets they always use. The major defense comes from the skin – it has a resistance of about 5,000 to 15,000 ohms. The clothes people wear add to the resistance of their skin. To break through such a formidable resistance, the static shock necessary just only to sting your skin is about 20,000 Volts. However, a person may not die from high-voltage electric shock if the electricity did not pass through the heart. If it traveled along the outside of their body, they would live, but likely with a scorched skin. This happens mostly when the skin is wet.

A lightning bolt is a different game altogether. One bolt of lightning can hit with over a billion volts. The resistance air offers to electricity is about 10,000 volts per centimeter. Therefore, for electricity simply to move current through 10 cm of air, the voltage required is 100,000 volts, and this is between the cloud generating the electricity and the earth below our feet. As high-voltage electricity or lightning takes the path of the least resistance when passing to the earth, it passes through the outer surface of the body, scorching the skin.