Why do electrical overhead wires hang loosely instead of being stretched tightly?
Electrical wires are made up of copper which is a metal, metals conduct heat and electricity. The main reason they conduct heat and electricity is because they have additional electrons , when heat is applied it provides energy to these electrons, this additional energy makes them move out of their original shell thus expanding the atom structure. This overall expansion of the shells makes the entire wire expand to a certain extent. Similarly the exact opposite is the case when metal is cooled ie at night, the atoms receive less or no energy from the sun this makes them go back to a more stable state and thus contracting to it's initial or even to smaller size depending on the surrounding temperature. Because of this phenomena the wire undergoes expansion and contraction every single day, thus if the wires were tightly held in the long run the wires might get snapped because of the contraction it faced. Similar is the case in railway tracks where they place small gap between two joints of the track to allow it to expand during daytime. Hope this clears it.
What are some technical questions asked during an interview in a core electrical engineering company?
First of all, there are not any fixed questions which are asked in interview. All depends on the Interviewer and how you respond to the questions asked by him.Some tips which you should take care of:Never underestimate yourself. You are much capable of performing in an interview than you think. So just be calm and composed.Keep all basic concepts of Electrical Engineering clear. This is the only key to crack the Interview. No one is going to ask you anything in detail. So your basics is weak, start preparing for it. Here is the book which you should buy for brushing up your basic concepts of Electrical Engineering.Buy Objective Electrical Technology Book Online at Low Prices in IndiaBefore entering the room for interview, take deep breath and just be calm. This will boost your confidence.Be honest in writing Resume. Because 2–3 questions will be directly from it.Here comes the main part,What are the questions asked?Introduce YourselfQuestions from Resume i.e. about your training and final year project.What is difference between Isolator and Circuit Breaker?Difference between MCB and MCCB.What is D.C Generator?What are your favorite subjects?What is Electric Traction?What is Current Transformer?In transformers, what remains constant?Draw waveform of D.C Frequency. This will check your presence of mind.What will happen if 40 Hz is provided to Transformer?Applications of D.C Series Motor.So you can see all the questions asked are not that tough. Just be confident and don’t be Nervous. Good Luck!!
When working on live electrical circuits - keep one hand on your hip or in your pocket?
Because your heart is between your arms. Electricity always takes the shortest path. If you grab two wires, one with each hand, what's the shortest path between those wires? Through your arms and through your chest (including your heart). So if you grab two wires of the opposite polarity, you'll get electrocuted. When this happens, the electricity goes through your heart, which can cause it to stop or even burn (depending on the amount of current), thus making you die. If you're going to get electrocuted, you want the electricity to go down your side, not between your arms. By holding wires with only one hand and touching nothing but your own self with the other, if you get zapped, the electricity will go through your arm, down your side, and through your foot, rather than through your heart. You could still get very badly injured, but you won't be killed instantly. Note: don't use your body to determine if a circuit is live. That's a good way to get killed. Go to a hardware store, and buy a voltmeter.
How difficult is rewirig the electrical in a house with multiple floors?(no experience)?
It would be difficult, if you have no experience working with electricity, and yes as mentioned dangerous. More people are killed by 110 vac, than any other voltage so be extra cautious. I know a couple people who have done some very bad wiring, which could have led to a fire, or someone getting electrocuted if they were touching a light that was energized. One of these was an engineer, so you can't depend on a persons level of schooling. It's better left to someone who really knows electricity. A licensed electrician can be expensive, but worth it if you don't know someone you can trust. I do all my own work at my house, (it's not illegal) but I have a lifetime of experience working with electricity even though I have not pursued and obtained a license. I was an electrician in the US NAVY, and I have worked with electricity at my job for 25 years. I trust my own work, and a couple others who are also un-licensed, but other than that, I wouldn't let anyone else but a licensed electrician work on my house.
Will touching a neutral wire render an electric shock? Why?
A lot of technical answers here but here is a real life answer.I am an Electrician.I have touched a neutral wire many times and have never been shocked. It all depends if there is a load on it. The neutral is the return path back to earth after the electricity travels thru the load.( light, motor, computer….) With no load, there is no potential (voltage) on the neutral under normal circumstances.If you touch the neutral wire and there is a load on it, you may receive a shock depending on if you are grounded or not. Electricity has to have a place to go and is trying to get back to earth. If you are not grounded then it will not flow thru you.If the neutral circuit is “open” meaning that the circuit is broken somewhere, and you inadvertently complete the circuit thru your body, you will get one nasty shock. In fact, some of the worst shocks I have received have been from open neutrals in junction boxes or light fixtures.If you touch the neutral buss in your electrical panel, you should not get shocked. It is the same potential as ground….if your system was installed correctly.PLEASE DONT TRY THIS AT HOME!!! Don't try any of the scenarios above. A shock can be mildly irritating to fatal under the correct circumstances. Please keep these theories just theories.
How do you safely wire an electrical outlet?
Get a qualified electrician to do it. That's the safest way.If not, switch all power off, at the main isolator.You need to calculate the current load, and select the cable accordingly. Undersized cable on high current loads, will cause fire, and compromise your safety.You also need to be colour literate, because you need to know what colour goes to where. Depending on what country you live in, also depends what wire colours, that will be available to you, as every country has their own colour scheme.Figure out where you intend to take the supply from. Is the supply a spur, or a ring? Does this circuit have enough current for my new outlet?You need to drill holes to mount the back box, or chisel the wall to sink the back box into it. An outlet should be fixed to a solid object, and not allowed to suffer any tension from tripping over, or pulling any connected devices.If you do not understand these basic things, I would highly advise you contact a qualified electrician to install the outlet for you.Being unqualified, you automatically compromise your own, and your households/workplaces electrical safety.
200amp service required materials list question.?
**** Before you tell me electrical work should be left to the professionals I AGREE with you and dont plan on doing any of the work myself. I have a friend who is a licensed electrician who owes me a favor and will do the work for me but is currently away travelling. I am only asking this because I am trying to estimate the materials ***** All of this work relates to an underground transformer and then running a span of 150 feet underground enclosed in a proper electrical conduit coming through to the foundation. I have a list of materials that im thinking, could you reference the letter if you would add/change/delete the items, a) 200 amp meter base station b) Shut off switch geared for 200 amps c) (17) 10' pieces of 3" electrical conduit to cover the 150' span plus additional 20' for connecting to transformer and bringing conduit up through foundation into service panel. d) Various assortment of 90s 45s, etc + cement for conduit e) 170' of 4/0-4/0-2/0 aluminum Urd Cable f) 200 amp cutler hammer panel g) 10' copper ground bar + clamp + span of 2/0 wire h) ground terminal strip to go in panel i) neutral terminal strip to go in panel j) various circuit breakers + romex + romex connectors **** Before you tell me electrical work should be left to the professionals I AGREE with you and dont plan on doing any of the work myself. I have a friend who is a licensed electrician who owes me a favor and will do the work for me but is currently away travelling. I am only asking this because I am trying to estimate the materials ***** 1) Is that 4/0 4/0 2/0 aluminum cable sufficient? 2) Am I forgetting anything? TY
Is running larger appliances off 240v more efficient than 120v?
1st off most appliances can not have there voltages switched. To find out the total wattage used you need to use this formula Watts = Volts x Amps to find out your wattage you also need to know the amperage of the appliance. The amperage also depends on the load (amount of work the motor is put under) it's like a electric heater with different heat settings the low setting uses less wattage and puts out less heat the high setting uses more wattage and puts out more heat but, the voltage will stay the same. So to find out the Wattage you need this formula Watts = Volts x Amps