Battery question.

kW or W Are you sure it's 746kwh or just 746 watts. How many horsepower
is your vacuum cleaner, garbage disposal?

"Kevin DeAngelis" > wrote in message
news:5yqpd.9214$ld2.8677@trnddc05...
| Whoops - meant to say that 1 horsepower-hour equals ).746 kwh. Sorry.
|
| "Kevin DeAngelis" > wrote in message
| news:Rvqpd.9213$ld2.6911@trnddc05...
| > Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower
is
| > *not* a unit of energy, but horsepower-hours are.
| >
| > You may be more familiar with the watt as a unit of power, and a
| > kilowatt-hour as a unit of energy. One horsepower is equal to 746
watts.
| > One horsepower-hour is equal to 1 kilowatt-hour. Electric utilities
will
| > bill you for energy used in kilowatt-hours. They don't bill for
| > kilowatts.
| >
| > Torque is a unit of force over distance, for example newton-meters or
| > foot-pounds.
| >
| > These concepts are easily confused. In addition to working as an
engineer
| > for an electric utility, I occasionally teach electric circuits and
| > statics classes at the local community college. I find that students
| > confuse power, energy and torque frequently.
| >
| >
| > "Fred W" > wrote in message
| > ...
| >> Kevin DeAngelis wrote:
| >>
| >>> However, unlike a horsepower rating, which is an instantaneous
quantity,
| >>> amp-hours represent energy (which is power over time), divided by
| >>> voltage.
| >>
| >>
| >> Bzzzzt! Wrong answer...
| >>
| >> Horsepower is a unit of work over time.
| >> Torque is the instantaneous measurement.
| >>
| >> <http://vettenet.org/torquehp.html>
| >>
| >> But thanks for playing!
| >>
| >> -Fred W
| >
| >
|
|

1 hp = 746 watts= 0.746 kW


"John Riggs" > wrote in message
...
> kW or W Are you sure it's 746kwh or just 746 watts. How many horsepower
> is your vacuum cleaner, garbage disposal?
>
> "Kevin DeAngelis" > wrote in message
> news:5yqpd.9214$ld2.8677@trnddc05...
> | Whoops - meant to say that 1 horsepower-hour equals ).746 kwh. Sorry.
> |
> | "Kevin DeAngelis" > wrote in message
> | news:Rvqpd.9213$ld2.6911@trnddc05...
> | > Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower
> is
> | > *not* a unit of energy, but horsepower-hours are.
> | >
> | > You may be more familiar with the watt as a unit of power, and a
> | > kilowatt-hour as a unit of energy. One horsepower is equal to 746
> watts.
> | > One horsepower-hour is equal to 1 kilowatt-hour. Electric utilities
> will
> | > bill you for energy used in kilowatt-hours. They don't bill for
> | > kilowatts.
> | >
> | > Torque is a unit of force over distance, for example newton-meters or
> | > foot-pounds.
> | >
> | > These concepts are easily confused. In addition to working as an
> engineer
> | > for an electric utility, I occasionally teach electric circuits and
> | > statics classes at the local community college. I find that students
> | > confuse power, energy and torque frequently.
> | >
> | >
> | > "Fred W" > wrote in message
> | > ...
> | >> Kevin DeAngelis wrote:
> | >>
> | >>> However, unlike a horsepower rating, which is an instantaneous
> quantity,
> | >>> amp-hours represent energy (which is power over time), divided by
> | >>> voltage.
> | >>
> | >>
> | >> Bzzzzt! Wrong answer...
> | >>
> | >> Horsepower is a unit of work over time.
> | >> Torque is the instantaneous measurement.
> | >>
> | >> <http://vettenet.org/torquehp.html>
> | >>
> | >> But thanks for playing!
> | >>
> | >> -Fred W
> | >
> | >
> |
> |
>
>

Thanks, I didn't think I was nuts....of course it is standard measure
for most technical disciplines. Mine happens to be computers and
electronics.

"Kevin DeAngelis" > wrote in message
news:FKzpd.5631$Rs2.3083@trnddc03...
|1 hp = 746 watts= 0.746 kW
|
|
| "John Riggs" > wrote in message
| ...
| > kW or W Are you sure it's 746kwh or just 746 watts. How many
horsepower
| > is your vacuum cleaner, garbage disposal?
| >
| > "Kevin DeAngelis" > wrote in message
| > news:5yqpd.9214$ld2.8677@trnddc05...
| > | Whoops - meant to say that 1 horsepower-hour equals ).746 kwh. Sorry.
| > |
| > | "Kevin DeAngelis" > wrote in message
| > | news:Rvqpd.9213$ld2.6911@trnddc05...
| > | > Sorry Fred, but I'm afraid that you are wrong on this one.
Horsepower
| > is
| > | > *not* a unit of energy, but horsepower-hours are.
| > | >
| > | > You may be more familiar with the watt as a unit of power, and a
| > | > kilowatt-hour as a unit of energy. One horsepower is equal to 746
| > watts.
| > | > One horsepower-hour is equal to 1 kilowatt-hour. Electric utilities
| > will
| > | > bill you for energy used in kilowatt-hours. They don't bill for
| > | > kilowatts.
| > | >
| > | > Torque is a unit of force over distance, for example newton-meters
or
| > | > foot-pounds.
| > | >
| > | > These concepts are easily confused. In addition to working as an
| > engineer
| > | > for an electric utility, I occasionally teach electric circuits and
| > | > statics classes at the local community college. I find that
students
| > | > confuse power, energy and torque frequently.
| > | >
| > | >
| > | > "Fred W" > wrote in message
| > | > ...
| > | >> Kevin DeAngelis wrote:
| > | >>
| > | >>> However, unlike a horsepower rating, which is an instantaneous
| > quantity,
| > | >>> amp-hours represent energy (which is power over time), divided by
| > | >>> voltage.
| > | >>
| > | >>
| > | >> Bzzzzt! Wrong answer...
| > | >>
| > | >> Horsepower is a unit of work over time.
| > | >> Torque is the instantaneous measurement.
| > | >>
| > | >> <http://vettenet.org/torquehp.html>
| > | >>
| > | >> But thanks for playing!
| > | >>
| > | >> -Fred W
| > | >
| > | >
| > |
| > |
| >
| >
|
|

Kevin DeAngelis wrote:
> Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is
> *not* a unit of energy, but horsepower-hours are.

Yep, you're right. I was wrong.

> Torque is a unit of force over distance, for example newton-meters or
> foot-pounds.

But the distance is not the distance of the work, but rather it's the
distance of the leverage applying the force to convert it to rotational
energy, right?

-Fred W

Fred:

By "the distance of the leverage", I think you mean the moment arm. That's
the length of a wrench handle, for example. If I apply 100 lb. of force to
a 1 ft moment arm, I get 100 ft-lb. If I have a five foot moment arm (like
a breaker bar), I only need to apply 20 lb. of force to get that same 100
ft. lb.

So yes, you're correct - when we say force over distance, that distance is
indeed the length of the moment arm.

Kevin

"Fred W" > wrote in message
...
> Kevin DeAngelis wrote:
>> Sorry Fred, but I'm afraid that you are wrong on this one. Horsepower is
>> *not* a unit of energy, but horsepower-hours are.
>
> Yep, you're right. I was wrong.
>
>> Torque is a unit of force over distance, for example newton-meters or
>> foot-pounds.
>
> But the distance is not the distance of the work, but rather it's the
> distance of the leverage applying the force to convert it to rotational
> energy, right?
>
> -Fred W

Yeah, and I didn't help matters any by typing a parenthesis instead of a
zero!

"John Riggs" > wrote in message
...
> Thanks, I didn't think I was nuts....of course it is standard measure
> for most technical disciplines. Mine happens to be computers and
> electronics.
>
> "Kevin DeAngelis" > wrote in message
> news:FKzpd.5631$Rs2.3083@trnddc03...
> |1 hp = 746 watts= 0.746 kW
> |
> |
> | "John Riggs" > wrote in message
> | ...
> | > kW or W Are you sure it's 746kwh or just 746 watts. How many
> horsepower
> | > is your vacuum cleaner, garbage disposal?
> | >
> | > "Kevin DeAngelis" > wrote in message
> | > news:5yqpd.9214$ld2.8677@trnddc05...
> | > | Whoops - meant to say that 1 horsepower-hour equals ).746 kwh.
> Sorry.
> | > |
> | > | "Kevin DeAngelis" > wrote in message
> | > | news:Rvqpd.9213$ld2.6911@trnddc05...
> | > | > Sorry Fred, but I'm afraid that you are wrong on this one.
> Horsepower
> | > is
> | > | > *not* a unit of energy, but horsepower-hours are.
> | > | >
> | > | > You may be more familiar with the watt as a unit of power, and a
> | > | > kilowatt-hour as a unit of energy. One horsepower is equal to 746
> | > watts.
> | > | > One horsepower-hour is equal to 1 kilowatt-hour. Electric
> utilities
> | > will
> | > | > bill you for energy used in kilowatt-hours. They don't bill for
> | > | > kilowatts.
> | > | >
> | > | > Torque is a unit of force over distance, for example newton-meters
> or
> | > | > foot-pounds.
> | > | >
> | > | > These concepts are easily confused. In addition to working as an
> | > engineer
> | > | > for an electric utility, I occasionally teach electric circuits
> and
> | > | > statics classes at the local community college. I find that
> students
> | > | > confuse power, energy and torque frequently.
> | > | >
> | > | >
> | > | > "Fred W" > wrote in message
> | > | > ...
> | > | >> Kevin DeAngelis wrote:
> | > | >>
> | > | >>> However, unlike a horsepower rating, which is an instantaneous
> | > quantity,
> | > | >>> amp-hours represent energy (which is power over time), divided
> by
> | > | >>> voltage.
> | > | >>
> | > | >>
> | > | >> Bzzzzt! Wrong answer...
> | > | >>
> | > | >> Horsepower is a unit of work over time.
> | > | >> Torque is the instantaneous measurement.
> | > | >>
> | > | >> <http://vettenet.org/torquehp.html>
> | > | >>
> | > | >> But thanks for playing!
> | > | >>
> | > | >> -Fred W
> | > | >
> | > | >
> | > |
> | > |
> | >
> | >
> |
> |
>
>

Definitions of Cold Cranking Amps on the Web:

A performance rating for automobile starting batteries. It is defined as
the current that the battery can deliver for 30 seconds and maintain a
terminal voltage greater than or equal to 1.20 volts per cell, at 0degrees
Fahrenheit (-18Celsius), when the battery is new and fully charged. Starting
batteries may also be rated for Cranking Amps, which is the same thing but
at a temperature of 32F (0C).

Kevin DeAngelis wrote:
> Fred:
>
> By "the distance of the leverage", I think you mean the moment arm. That's
> the length of a wrench handle, for example. If I apply 100 lb. of force to
> a 1 ft moment arm, I get 100 ft-lb. If I have a five foot moment arm (like
> a breaker bar), I only need to apply 20 lb. of force to get that same 100
> ft. lb.
>
> So yes, you're correct - when we say force over distance, that distance is
> indeed the length of the moment arm.
>

Thanks. One more thing, and I appreciate your patience with me...

Most of the "definitions" I see about horsepower include the element of
time in the calculation. example: one HP = 33,000 ft/lbs per minute.
Yet you have indicated (and I have found some corroboration)that
horsepower is a measurement of power and does not express "power
consumption".

How can this be if the formula for horsepower already contains the
element of time in it?

-Fred W

Fred, glad to help. I enjoy helping others learn, which is why I teach
classes occasionally. And as I said, these concepts are easy to confuse.

First of all, 1 hp = 33,000 ft-lb/min, not ft/lbs per minute. That's
important because you can get a good idea of the relationship between these
quantities from their units.

Remember that the units of torque are ft-lb (force multiplied by distance).
Since horsepower has the units of ft-lb per minute, then this tells you that
horsepower is torque divided by time. Mathematically, this means that if
you draw a curve with torque on one axis versus time on the other axis, and
took the first derivative of that curve with respect to time, you would get
the horsepower at that instant in time. If calculus isn't familiar to you,
another way to say it is that if you take the slope of the torque curve (by
drawing a straight line tangent to the curve at an arbitrary point on the
curve), that gives you the horsepower at that point in time. If you take
the slope at every point on the torque curve, you end up with the horsepower
curve.

It's the same thing as the relationship between distance (meters), velocity
(meters/sec) and acceleration (meters/sec squared).

Since we know that power multiplied by time equals energy (kilowatt-hours,
for example), and if torque divided by time equals horsepower (ft-lb/min),
you realize that torque has units of energy. That's where the time
relationship comes in. If you study engineering, you find that distance,
time, energy, power, etc., are more interrelated than is intuitively
obvious. So horsepower-hours and Newton-meters are both units of energy.
In fact, according to my references, one hp-hour equals 2,684,520
Newton-meters.

There's a really good little conversion program available, called
convert.exe. You can get it for free at
http://www.joshmadison.com/software/convert/. I use this program at home
and at work.

I hope that this makes sense. If you want more help, drop me an email at
. I imagine that most everyone else is rolling their
eyes or sound asleep by now!

Cheers,
Kevin

"Fred W" > wrote in message
...
> Kevin DeAngelis wrote:
>> Fred:
>>
>> By "the distance of the leverage", I think you mean the moment arm.
>> That's the length of a wrench handle, for example. If I apply 100 lb. of
>> force to a 1 ft moment arm, I get 100 ft-lb. If I have a five foot
>> moment arm (like a breaker bar), I only need to apply 20 lb. of force to
>> get that same 100 ft. lb.
>>
>> So yes, you're correct - when we say force over distance, that distance
>> is indeed the length of the moment arm.
>>
>
> Thanks. One more thing, and I appreciate your patience with me...
>
> Most of the "definitions" I see about horsepower include the element of
> time in the calculation. example: one HP = 33,000 ft/lbs per minute.
> Yet you have indicated (and I have found some corroboration)that
> horsepower is a measurement of power and does not express "power
> consumption".
>
> How can this be if the formula for horsepower already contains the element
> of time in it?
>
> -Fred W

Mathematically, this means that if
you draw a curve with torque on one axis versus time on the other axis, and
took the first derivative of that curve with respect to time, you would get
the horsepower at that instant in time

Darn - made a small boo-boo. If you draw a curve with torque on one axis
versus time on the other axis, and
took the first derivative of that curve with respect to time, you'd get a
continuous horsepower curve, over the same length of time. Sorry about
that.

Kevin