Q.s. Fuelless Generators Inc.

Four process color (CMYK) in any sized advertisement is a flat rate of $185 per insertion. For inserts, and current subscriber/circulation demographics, please call us.

Home Power is published bi-monthly. The ad deadline for the Feb / Mar 99 issue (HP69) is 21 Dec, 1998. Call 530-475-3179 for further details.

International Home Power Subscriptions

Due to the high cost of international mailing, we charge more for Home Power international subscriptions.

1 YEAR (6 issues) INTERNATIONAL RATES:

All payments in U.S. currency ONLY!

Canada: Mexico:

Western Hemisphere: Europe:

Asia and Africa: Pacific Rim:

Air — $36 Air — $38 Air — $40 Air — $53 Air — $64 Air — $64

Surface — $30 Surface — $30 Surface — $30 Surface — $30 Surface — $30 Surface — $30

Surface shipment may take up to three months. All international issues are shipped in mailing envelopes. International subs are best paid for by either VISA, MasterCard, or funds from a U.S. bank.

International orders:

Call: 530-475-0830 Fax: 530-475-0941

MicroAds

MicroAd rates are 100 per character. Characters include letters, numbers, spaces, and punctuation marks. $15 minimum per MicroAd insertion. Send a check with your ad. We do not bill MicroAds.

Home Power magazine for Resale

Quantities of Home Power Magazine are available for resale by distributors, newsstands, bookstores, energy businesses, and others. Please call, email, or write for rates and shipment specifics.

Back Issues of Home Power magazine

Back issues through #20 are $3.25 each ($4.25 each outside USA) while they last. Sorry, no more issues #1-10, 12, 14, 15, 16, 35, 36, 38, 40, 41, 59,or 60. Back issues of #21-45 are $4.75 each ($6 each outside USA). Back issues #46-current are $5.75 each ($7.25 outside USA). Back issues are shipped First Class mail in an envelope or box. See the ad index for current Home Power back issue specials. Issues #1-42 & #43-60 on CD-ROM for $29 each (US$32 outside USA) Win/Mac/Unix.

First Class Home Power Subscription

Get 6 issues of Home Power magazine via First Class U.S. Domestic Mail for $36. Many of you have asked for faster delivery, so here it is: First Class Home Power. All First Class issues shipped in an envelope. We start your subscription immediately with the current issue.

Second Class Home Power Subscription

Get 6 issues of Home Powervia Second Class U.S. Domestic Mail for $22.50. Second Class can be forwarded for one issue (2 months), so let us know immediately if you move! We start your sub with the next scheduled issue, so please allow ten weeks for your first copy to arrive.

ACCESS "■«► Home Power, PO Box 520, Ashland, OR 97520 USA 800-707-6585 or 530-475-0830 Subscriptions and Back Issues ^^ 3 . 530-475-3179 Advertising and Editorial. Web: www.homepower.com

Word Power

Renewable Energy Terms

Volt—Unit of electromotive force

Ian Woofenden

©1998 Ian Woofenden

Derivation: Named after Alessandro Volta, the Italian physicist who first invented the battery. The volt received official recognition as the unit of electrical potential in 1881.

Voltage is an electrical concept that is frequently misunderstood. In simple terms, it is electrical "pressure," analogous to pressure in a garden hose or a bicycle tire. It is also called "potential" or "potential difference."

If I said I might drop a piano on you from my 34th floor apartment, you'd know that it would hurt more when it hit you than if I only dropped it from my cousin's apartment on the 5th floor. However, knowing what floor I'm on would not tell you whether I have a concert grand, a spinet, or my child's toy plastic piano ready to drop. And you wouldn't even be sure that I would indeed drop it, only that it's possible. Likewise, voltage in itself tells us nothing about the flow rate (current) or the total quantity of electricity (though it does have a relationship to them). Voltage is roughly analogous to how many floors up my piano is, compared to a piano sitting on the sidewalk below.

Voltage is not flow rate, and it is not volume. We can measure high voltage when there is very little electricity available, and low voltage when there is a virtually unlimited supply. A capacitor the size of your fingernail can be charged to a potential of ten thousand volts, but the current flow when you discharge it will be minuscule. We can measure high pressure in a bicycle tire, but there is relatively little air there. On the other hand, a huge tractor tire can have a lot of air in it, but it may be at a fairly low pressure.

Let's not say that a PV module "produces" 17 volts, since having voltage doesn't necessarily mean you have electricity flowing. When you put your multimeter leads on the terminals of the PV, you are only reading the potential difference between the two points. Voltage alone doesn't give you the whole picture, and should not be confused with current, power, or energy. Current, which is measured in amperes, will be the topic for next time.

Access

Author: Ian Woofenden, PO Box 1001, Anacortes, WA 98221 • [email protected]

MINI 12/8

n ? rnciQucTs USR

OWTTlTra 1 iwwiq. IBHI ILUT* PLrtCK^UrtnTTTfcY Htr^nuc

MINI 12/8

Low Cost. High Performance 8 amp PWM Charge Controllers.

Ideal for RV's, marine, commercial applications. For all battery types & chemistries. Five year warranty Available world wide

7614 Marion Ct., St. Louis, MO 63143, USA

tel: 314-644-2490, fax 314-644-6121 e-mail: [email protected]

^JpPlanet DC

Now! RParts carries Planet DC refrigerators and freezers. We have everything to meet all your refrigeration needs at RPrices. Guaranteed lowest.

Call 800-720-3907 for a brochure

0 0

Post a comment