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Is it easier to generate static electricity in a dry room or a humid room?
Wiki User
∙ 11y ago
When the air is dry, static electricity is enhanced and more noticeable because of the easiness in transfer of electrons.
Wiki User
∙ 11y ago
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When is the build up of static electricity indoors usually greatest?
The build up of static electricity indoors is usually greatest in the winter time when indoor heat is on. The home heating drys the air in the house and with a lower humidity the static build up does not dissipate as well as higher humid air will.
How is electricity caused?
You walk across the rug, reach for the doorknob and..........ZAP!!! You get a static shock. Or, you come inside from the cold, pull off your hat and......BOING!!! Static electricity makes your hair stand on end. What is going on here? And why do static problems only seem to happen in the winter? To understand static electricity, we have to learn a little bit about the nature of matter. Or in other words, what is all the stuff around us made of? EVERYTHING IS MADE OF ATOMS Imagine a pure gold ring. Divide it in half and give one of the halves away. Keep dividing and dividing and dividing. Soon you will have a piece so small you will not be able to see it without a microscope. It may be very, very small, but it is still a piece of gold. If you could keep dividing it into smaller and smaller pieces, you would finally get to the smallest piece of gold possible. It is called an atom. If you divided it into smaller pieces, it would no longer be gold. Everything around us is made of atoms. Scientists so far have found only 115 different kinds of atoms. Everything you see is made of different combinations of these atoms. PARTS OF AN ATOM So what are atoms made of? In the middle of each atom is a "nucleus." The nucleus contains two kinds of tiny particles, called protons and neutrons. Orbiting around the nucleus are even smaller particles called electrons. The 115 kinds of atoms are different from each other because they have different numbers of protons, neutrons and electrons. It is useful to think of a model of the atom as similar to the solar system. The nucleus is in the center of the atom, like the sun in the center of the solar system. The electrons orbit around the nucleus like the planets around the sun. Just like in the solar system, the nucleus is large compared to the electrons. The atom is mostly empty space. And the electrons are very far away from the nucleus. While this model is not completely accurate, we can use it to help us understand static electricity. (Note: A more accurate model would show the electrons moving in 3- dimensional volumes with different shapes, called orbitals. This may be discussed in a future issue.) ELECTRICAL CHARGES Protons, neutrons and electrons are very different from each other. They have their own properties, or characteristics. One of these properties is called an electrical charge. Protons have what we call a "positive" (+) charge. Electrons have a "negative" (-) charge. Neutrons have no charge, they are neutral. The charge of one proton is equal in strength to the charge of one electron. When the number of protons in an atom equals the number of electrons, the atom itself has no overall charge, it is neutral. ELECTRONS CAN MOVE The protons and neutrons in the nucleus are held together very tightly. Normally the nucleus does not change. But some of the outer electrons are held very loosely. They can move from one atom to another. An atom that looses electrons has more positive charges (protons) than negative charges (electrons). It is positively charged. An atom that gains electrons has more negative than positive particles. It has a negative charge. A charged atom is called an "ion." Some materials hold their electrons very tightly. Electrons do not move through them very well. These things are called insulators. Plastic, cloth, glass and dry air are good insulators. Other materials have some loosely held electrons, which move through them very easily. These are called conductors. Most metals are good conductors. How can we move electrons from one place to another? One very common way is to rub two objects together. If they are made of different materials, and are both insulators, electrons may be transferred (or moved) from one to the other. The more rubbing, the more electrons move, and the larger the static charge that builds up. (Scientists believe that it is not the rubbing or friction that causes electrons to move. It is simply the contact between two different materials. Rubbing just increases the contact area between them.) Static electricity is the imbalance of positive and negative charges. OPPOSITES ATTRACT Now, positive and negative charges behave in interesting ways. Did you ever hear the saying that opposites attract? Well, it's true. Two things with opposite, or different charges (a positive and a negative) will attract, or pull towards each other. Things with the same charge (two positives or two negatives) will repel, or push away from each other. A charged object will also attract something that is neutral. Think about how you can make a balloon stick to the wall. If you charge a balloon by rubbing it on your hair, it picks up extra electrons and has a negative charge. Holding it near a neutral object will make the charges in that object move. If it is a conductor, many electrons move easily to the other side, as far from the balloon as possible. If it is an insulator, the electrons in the atoms and molecules can only move very slightly to one side, away from the balloon. In either case, there are more positive charges closer to the negative balloon. Opposites attract. The balloon sticks. (At least until the electrons on the balloon slowly leak off.) It works the same way for neutral and positively charged objects. So what does all this have to do with static shocks? Or static electricity in hair? When you take off your wool hat, it rubs against your hair. Electrons move from your hair to the hat. A static charge builds up and now each of the hairs has the same positive charge. Remember, things with the same charge repel each other. So the hairs try to get as far from each other as possible. The farthest they can get is by standing up and away from the others. And that is how static electricity causes a bad hair day! (Get tips on how to eliminate static electricity problems in your home or office.) As you walk across a carpet, electrons move from the rug to you. Now you have extra electrons and a negative static charge. Touch a door knob and ZAP! The door knob is a conductor. The electrons jump from you to the knob, and you feel the static shock. We usually only notice static electricity in the winter when the air is very dry. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you can not build up as big a static charge.
Can high tension wires emit any sound audible to the human ear?
I drove under high tension wires in a truck and could clearly hear a buzzing noise. I actually stopped the truck and sat under the wire for a moment to listen to the sound. As I recall it was a very humid day. I don't know if this is true but suspect the damp air had something to do with it.
Is there a standard and safe range for insulation resistance of motors or it's dependent on type of motorsif 30 Mohm is safe for a motor with 1000 Mohm of insulation resistance in normal conditions?
"INSULATION resistance is not about standard nd safe range because resistance value depend upon the application for which we are providing it in what range the current flows." The answer above is incorrect. Application and current rating & range have nothing to do with insulation resistance. There are standards available for insulation resistance testing both in terms of the test procedure and the values. IEEE Standard 43 provides a basis for insulation resistance testing. Both NETA ATS (Acceptance Testing Specification) and NFPA 70B gives criteria for insulation resistance testing. Insulation Resistance (IR) testing, also known by the slang terms meggering or megging, is a procedure where the quality of the electrical insulation is evaluated to determine if it is acceptable for service. It is also used to compare against previous measured values to determine if there has been any degradation to the equipment being tested. In this case we are talking about motor insulation. The question deals with two comparative readings and wants to know if the value of 30 megohms is acceptable. First we should clarify the test methods and results. NETA ATS 2007. Section 7.15.1 covers AC induction motors and generators. The testing involved is broken down into those motors 200 hp (150 kw) and less, and those > 200 hp (150 kw). The test voltage value is based upon the voltage rating of the motor's winding and is found in table 100.1: Rating = 250V; Test Voltage = 500 VDC; Minimum Resistance = 25 megohms Rating = 600V; Test Voltage = 1000 VDC; Minimum Resistance = 100 megohms Rating = 1000V; Test Voltage = 1000 VDC; Minimum Resistance = 100 megohms Rating = 2500V; Test Voltage = 1000 VDC; Minimum Resistance = 500 megohms Rating = 5000V; Test Voltage = 2500 VDC; Minimum Resistance = 1000 megohms Rating = 8000V; Test Voltage = 2500 VDC; Minimum Resistance = 2000 megohms Rating = 15000V; Test Voltage = 2500 VDC; Minimum Resistance = 5000 megohms Rating = 25000V; Test Voltage = 5000 VDC; Minimum Resistance = 20,000 megohms Rating = 34500V; Test Voltage = 15000 VDC; Minimum Resistance = 100,000 megohms It is important to note that the values given are based on a standard temperature of 40C (or sometimes 20C depending on the engineer's specification). You must correct your readings to a standard temperature as the value on the insulation's resistance is going to vary inversely with temperature. That is as temperature increases the resistance will decrease. The rule of thumb is that the measured value will halve for every 15C above standard and will double for every 15C below standard. As an example let us say that we have a 25 hp induction motor rated 480 VAC. The ambient temperature is 15C. Using our table we would set the tester to 1000 VDC and take a reading for one minute. At the end of the minute we get a reading of 450 megohms. Per NETA ATS Table 100.14 the correction factor is 0.31 so IR = 450 megohms x .031 = 139.5 megohms. The minimum acceptable value is 100 so this motor is acceptable. On the flip side if the motor is in a very warm process area, say 50C, then temperature correction factor is 1.59 thus IR = 450 megohms x 1.59 = 716 megohms. As you can see the temperature makes a very large difference in the results! This discussion up to this point has been about a spot-reading check. However for a true check we want to know the Dielectric Absorption value. There are two different standard tests for Dielectric Absorption. The first is the Dielectric Absorption Ratio (DAR) and the second is the Polarization Index. DAR = Reading @ 60 sec / Reading @ 30 sec. Let us say that the 30 sec reading = 325 megohms and the 60 sec = 450 megohms. Thus: DAR = 450 megohms / 325 megohms = 1.38 The minimum DAR per NETA is 1.4 so this particular motor is borderline at best and should be investigated further. PI = Reading @ 10 min / Reading @ 1 min. Let us say that the 1 min reading = 450 megohms and the 10 min = 1100 megohms. Thus: PI = 1100 megohms / 450 megohms = 2.44 The minimum PI per NETA is 2.0 so in this case the motors is acceptable. One final factor that should be taken into consideration is Relative Humidity (RH). The amount of moisture present in the air also affects the measured test values. The more moisture then the lower the reading. There is no published standard correction factor for RH however when NETA Techs perform these tests then they always record the RH for baseline comparison. The bottom line is that the readings will vary based upon temperature and humidity. A reading on warm humid day may be acceptable whereas the same reading on a cold dry day may not. So the question asked here is unanswerable as there is not enough information given. What were the temperatures at the time of the readings? Was it dry during one and raining during the other? What does the person asking mean by "normal conditions"? I highly recommend that anyone interested in this subject get the free book "A Stitch in Time" by Biddle at: http://www.biddlemegger.com/biddle/Stitch-new.pdf Please note that I also changed the category from Health/pregnancy to Electrical Engineering.
What condition does static electricity work best?
humid
Static electricity in hair?
Static electricity in hair can cause it to feel dry and it may start floating away from your head. This usually happens when it is not very humid.
Why does electricity works differently on a hot humid day than on a cold dry day?
Because humid weather is more wet, but dry weather is dry, and static electricity does not stick to wet things.
Why you are likely to receive a shock after walking across a carpet when the air is dry than when the air is humid?
That shock is caused by static electricity, or the build-up of charge on an object. As you do something that will help build that charge (like scuff along a carpet), static electricity on your person increases. Water is a better conductor of electricity than dry air. In humid air, the static electricity will be slowly discharged as it contacts the water vapor. When there is no water vapor, the static electricity is not conducted away from your body as it builds up, and it accumulates. At some point, you come close to a good conductor of electricity - a metal object, for instance - and the built-up charge discharges.
When is build up of static electricity indoors the greatest?
The build up of static electricity indoors is usually greatest in the winter time when indoor heat is on. The home heating drys the air in the house and with a lower humidity the static build up does not dissipate as well as higher humid air will.
When is the building of static electricity indoors usually greatest?
The build up of static electricity indoors is usually greatest in the winter time when indoor heat is on. The home heating drys the air in the house and with a lower humidity the static build up does not dissipate as well as higher humid air will.
How does one produce static electricity?
When the air is dry static electricity is more enhanced and noticeable than when the air is humid. Things with the same charge repel each other. You can produce static electricity by rubbing a balloon in your hair. It will cause your hair to stand up and the balloon will be able to stick to a wall. Also if you have on rubber sole shoes and you drag them along a carpet the first person you touch will be shocked by static electricity.
Why is static electricity higher on a dry day than humid day?
Water molecules allows some electricity to constantly discharge. Only little humidity and the static electricity can grow to a quite high voltage. A lot of humidity will counteract this. As voltage increases, more will be dissipated by the moisture.
When is the build up of static electricity indoors usually greatest?
The build up of static electricity indoors is usually greatest in the winter time when indoor heat is on. The home heating drys the air in the house and with a lower humidity the static build up does not dissipate as well as higher humid air will.
Why is static electricity worse in the winter than the summer?
Frictional electricity is observed more in winter than summer because of the static electricity which happens more in winter than in summer. Static electricity usually results when to materials that are dissimilar are rubbed together.
Why is it difficult to demostrate the Coulomb's law on humid or moist day?
The Coulomb's Law kit is perfect for a dry and windy day, but works poorly on a humid, wet day. Enough viable data cannot be collected on a humid day as humid air discharges static electricity slowly.
Why is static higher on a dry day than a humid day?
Water molecules allows some electricity to constantly discharge. Only little humidity and the static electricity can grow to a quite high voltage. A lot of humidity will counteract this. As voltage increases, more will be dissipated by the moisture.
