Please Explain: Electricity

Friday, October 30, 2009

How does electricity get from its source into your home and to your cell phone charger, television, or microwave? We’ll find out on today’s Please Explain. Michael Caramanis, Boston University Professor of Mechanical and Systems Engineering, joins us, along with Dr. Robert Thomas, professor in the Department of Electrical and Computer Engineering at Cornell University.


Michael Caramanis, and Dr. Robert Thomas,

Comments [32]


Sadly, these were remarkably inaccessible guests. Lopate was very polite and asked straightforward questions. But neither guest answered those questions, such as the basic difference btwn AC and DC. Very convoluted answers to basic questions. Did they not know their audience? And while Caramanis was courteous and seemed friendly, Thomas came across as arrogant-sounding, as if certain questions were so simple, as to not require explanation. Then he proceeded to respond poorly to a question that had not been asked. I attended MIT, I've heard lucid and elegant explanations of science fundamentals that would suit an NPR audience and this was far from it, much too opaque.

Oct. 30 2009 03:24 PM
yourgo from Astoria

Yeiasou Caramanis! Bravo, great job representing greek genious on the show today..

Oct. 30 2009 03:16 PM
Nick from Upper West Side

Geez...these guys are completely useless.

Batteries are containers holding chemicals that when mixed together strip electrons off the molecules creating a negative potential within the chemical. When a power-drawing device is connected to the battery it gives the electrons in the chemicals a pathway to move, thus current flows.

Oct. 30 2009 02:01 PM
Mark from Dobbs Ferry

Speaking of 3rd world grids, I was running on a treadmill in a Jakarta gym 1990, at a pretty good clip (was much more fit then) when the power went out. Needless to say, such situation was pretty painful. The most painful of all, however, was my embarrassment after getting back on there only to have the same thing happen just 10 minutes later.

Oct. 30 2009 01:59 PM
Andy from Brooklyn

David [19], batteries contain two chemicals which want to exchange electrical charge, but can only do so when a path for the charge exchange is available. When you connect the terminals of the battery to a device which will draw power from it, you create that path. The chemicals then start handing off electrons to your device on one terminal, and collecting them from the other. Eventually all the chemicals are used up and you need to get a new battery.

An ideal battery would only use up the chemicals inside when the terminals are connected through a circuit. However, batteries are not perfect, and if left alone, the chemical process will slowly take place --- that is, a battery can't hold it's energy forever.

Oct. 30 2009 01:57 PM
Mark from New York City

Hmmm.... not the most 'electric' of guests, poor lenny! But moving on..... Wouldn't it be cheaper, in the long run, to install cables underground in non-urban areas as well, given the enormous cost of repairs every time there's a storm? Thanks.

Oct. 30 2009 01:54 PM
A.R. Rowe from New York, NY

Please comment on physical, safety (both claimed and real), and legal barriers to selling electricity back to the grid from rooftop solar or backyard wind.

Also, please explain how U.S. soldiers in Iraq were electrocuted in showers in living facilities built by private contractors. I know it's sloppy work or mistakes in construction, but I'm curious in what specifically was done or not done to endanger our soldiers in their living quarters.


Oct. 30 2009 01:51 PM
Nick from Upper West Side

Adam from NY - I think the better question would be "Is there rip-off or corruption somewhere in the power company's billing department?"

Oct. 30 2009 01:50 PM
Tom from Upper West Side

Gad, I'm glad I don't have to sit through these professors lectures!

Oct. 30 2009 01:50 PM
Dario from New York

We analyzed power converters in my Power Electronics course at Rutgers University. My profeesor told my class that although AC became the standard for powerlines, DC may come back because of digital technology. By switching DC voltages on and off at very high speeds Digital DC power can be as good oas AC power transfer.

Oct. 30 2009 01:48 PM
Adam from NY, NY

I have a usage monitor that keeps track of my monthly usage. Every month the amount on the monitor is about 25% lower than the billed amount. I have tested the device by turning on an appliance whose draw I know and it gives an accurate reading. So why is there a discrepancy between these readings? Is there electricity being wasted somewhere?

Oct. 30 2009 01:48 PM
Andy from Brooklyn

A question: what is the future of electricity supply? In 50 years, will we still be using large power plants and grids or will we start using more efficient in-home power production (through something like a fuel cell)?

Oct. 30 2009 01:47 PM
John A. from Ossining

re: The Power strip comment [4]:
Empty power strips may have a tiny light bulb in them that draw less than 1/10 watt. This applies to many things with this small lights in them - consider their power draw negligible.
Even a big VCR turned off with the digital clock
going may draw less than 1 watt.
Also effects questioner [1]

Oct. 30 2009 01:47 PM
david from montclair, nj

Can someone explain batteries? How or what is the electricity inside? Is there electricity going on inside all the time or dormant until placed in an appliance.

Oct. 30 2009 01:47 PM
Conrad Youngren from Yonkers

Robert, the high tension transmission lines are bare (stranded aluminum with a few steel strands for strength). The "local" lines are usually insulated copper.

Oct. 30 2009 01:45 PM
Nick from Upper West Side

Andy - Of course. But really, these guys could have been so much more informative and clear.

Oct. 30 2009 01:41 PM
Andy from Brooklyn

The charger is not an open circuit. The portion of the circuit after conversion form AC to DC might be open, the converter is closed. If your charger heats up, even when not plugged into the device it's charging, then it's definitely drawing juice.

Oct. 30 2009 01:41 PM
John A. from Ossining

I live just 7 miles from a major generating facility yet the last time
there was a statewide grid failure all they could do was to shut down the
local plant and spend many hours planning how to put all the plants back
online. Will so-called smart grid technology make this a thing of the past?

Oct. 30 2009 01:40 PM
Roberr Plaut from NJ

Thee guys are not really answering your questions. Here's my question:

If the generators make more electricity than we need at the time, can it be stored somehow until it is needed? (like oil can be stored in a tank).

Of course the power lines are made of metal.

What kind of metal?

Are these power line bare?

How long do they last?

Oct. 30 2009 01:40 PM
Conrad Youngren from Yonkers

Wow, that description of electricity from steam was obtuse. If the wind turning a device (conductors in way of a magnet) is not a conceptual problem, then blowing steam through a similar device should not be mysterious. And the pressure & velocity of the steam can be controlled (which the wind can't,thus controlling the rate of electrical generation. That steam comes from boiling water which requires heat., thus the variety of primary sources: burning fossil fuels, nuclear fission, geothermal, solar, etc.

Oct. 30 2009 01:40 PM
Nick from Upper West Side

Lennie - If a charger is plugged in it draws power whether or not the cell phone or whatever is plugged into it. That's why you should unplug all that stuff like chargers if you are not using them; they hike up your electric bill.

Oct. 30 2009 01:40 PM
Ro from SoHo

Mr. Lopate, you are doing an admirable job with these very difficult guests. Both of them! The ums and ahs are not helpful, nor are the obtuse and bumbling explanations to your very clear and probing questions.

Oct. 30 2009 01:39 PM
Nick from Upper West Side

Hank - An outlet strip draws no power at all if you are not running anything off it. Even if you ARE running something off it, the strip itself draws no power. It is merely a conduit. The only exception is that sometimes an outlet strip has a little light or LED on it to show when it's on. This draws a tiny amount of power.

A lamp that is turned off is drawing no power whatsoever even if it's plugged in.

Oct. 30 2009 01:38 PM
Paul from United States


Maybe your Boston collegues don't know that the Brooklyn Dodger's got there name from DC current buildup on the early tram lines. Dodging became a regular activity then.

Oct. 30 2009 01:37 PM
Andy from Brooklyn

Nick, that's not the full story. There are solid-state solar energy sources that use the photoelectric effect to produce currents. There is also the chemical burning of fuels (in, say, Hydrogen fuel cells) that produce currents --- these methods are actually far more efficient than simple combustion.

Oct. 30 2009 01:37 PM
Lennie Florescue from Manhattan

Along the same lines - if a charger is plugged into the wall outlet, but not to blackberry or cell phone, is it drawing any electricity?

I would assume that, as the circuit is open, no current can flow - anymore than it comes out of the wall socket with nothing plugged in. My wife says she has heard on TV from "experts" who say there is power usage in that case.

Please comment. Thank you.

Oct. 30 2009 01:37 PM
Nick from Upper West Side

Typical professor....Leonard asks him a simple direct question "What is electricity?", something we'd all like to know. Instead of an answer, we get vague blather concerning electrical terminology and the question is left 100% unanswered.

The generation of electrical energy is simple: water is boiled using various heat sources; coal, oil, gas, nuclear reactor; and the steam is blown through turbines which turn generators that make the electricity. Or a water force such as a river is used to spin water-wheel turbines which then turn generators.

Why do these guys have to make everything so vague and tentative and overcomplicated?

Oct. 30 2009 01:33 PM
Gavin from Long Valley, NJ

Despite Leonard Lopate's polite and clear questions, neither of his guests are answering his basic questions. 'what is electricity?, 'how is it created?'. I begin to think they may not understand the basic physics behind electron stripping and movement. Can he probe some more?

Oct. 30 2009 01:33 PM
Hank from Brooklyn

If you have a power strip plugged into an outlet, even if you are'nt running anything, is that drawing power and increasing you electric bill ? or if a lamp is plugged in but turned off is it still drawing power ?

Oct. 30 2009 01:29 PM
Andy from Brookly

Geeeez... your guest is being overly complicated. You can imagine how your car or a steam engine works: how you can burn a fuel to get something to turn. If instead of having the wheel of your car at the end of that turning action, you have a loop of wire in a magnetic field, then the turning of that loop will provide an electric current.

Oct. 30 2009 01:29 PM
Frank Campi from Rockaway, Nj

Please comment on water use making electricity.

Oct. 30 2009 01:28 PM
Whitney Speer from North New Jersey

Please ask the experts to discuss "Vampire Electricity" or "Phantom Electricity" (appliances using electricity when they are turned off) and what we should believe about it. Should we have everything on Power Strips?

Thank you!

Oct. 30 2009 01:27 PM

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