Physics - April 2007

Copper and Aluminum are being considered for the cables in a high-voltage transmission line where each must carry a current of 50A. The resistance of each cable is to be .15ohms per kilometer.

A. If the line carries power from Niagra Falls to New York (500Km), mow much power is lost along the way in the cable?


Compute for each choice of cable material
B. the necessary cable diameter

C. mass per meter of cable

Please correct if you see anything that may be off
Solving for part a:
Power = I deltaV, since deltaV was not given IR=deltaV
so
Power = (I^2)R = 50^2 x 75 = 187.5 kW <-- answer
R= 75 since R= .15 ohms/ km x 500km

B) resistivity of copper = 1.7 x 10^-8 ohm m
resistivity of al = 2.82 x 10^-8 ohm m
R = (resistivity x length)/Area
what do i use for R? is it the 0.15 ohm/km or 75 ohm?

using the 75 ohm as R, I get that the radius of the copper wire is 0.0000361 m and the diameter is then 0.0000722.
Am i on the right track?

2007-04-08 04:17:32 · 4 answers · asked by ARE JAY 1

I read something that barely touched on it, but I thought was interesting. What are your thought on parallel universes being responsible for mental disorders such as multiple personalities, etc.?

2007-04-08 04:17:11 · 9 answers · asked by stephanie g 1

2007-04-08 03:17:40 · 6 answers · asked by anarchygirl 1

2007-04-08 03:13:24 · 13 answers · asked by alan p 2

Easter Guilt. What's the difference between void and chaos?
Dumb question, I know. Just woke up.
Thanks for your time and patience.

2007-04-08 03:04:15 · 3 answers · asked by Dovey 7

why?

2007-04-08 02:08:38 · 2 answers · asked by sochn9022jkl 1

2007-04-08 01:48:09 · 6 answers · asked by Anonymous

2007-04-07 19:59:25 · 3 answers · asked by Hanif 1

i am not puting up a joke...
seriously, how would anyone know if i was a genious?

2007-04-07 18:20:46 · 13 answers · asked by Anonymous

2007-04-07 17:30:26 · 7 answers · asked by ocean 1

i am a student of 10th standard

2007-04-07 17:22:59 · 4 answers · asked by VIVEK 1

2007-04-07 17:16:43 · 8 answers · asked by heesenlee 1

Air boils at -183C
Liquid nitrogen boils as -196C

2007-04-07 17:07:57 · 2 answers · asked by 3ajeeba_q8 2

A violin plays a melody line and is then joined by nine other violins, all playing at the same intensity as the first violin, in a repeat of the same melody.
(a) When all of the violins are playing together, by how many decibels does the sound level increase?
Answer: 10 dB.

Sooo....my question is...

(b) If ten more violins join in, by how many decibels does the sound increase over that for the single violin?

2007-04-07 16:53:04 · 2 answers · asked by Anonymous

I've tried lasers but they do not work out and i am very confused with the mirror idea. How can I use two mirrors to find the unknown distance between two objects? Can you please give a procedure? thanks

please note that there can be no direct measurement. All the measurements must be done before hand but there will be no measurements allowed at the time of the presentation. Calculations are allowed

what is meant by direct measurement is time, rulers, etc...

2007-04-07 16:16:44 · 3 answers · asked by anikabot 2

2007-04-07 16:00:16 · 12 answers · asked by Theo 2

I'm interested in enhancing the sterling motor. by using a vacuum to cause water to turn to ice thereby allowing for the contraction of the gas in the chamber. But I don't know if the water in the vacuum will stay cold when heat from the the gas is supplied to the vacuum packed container.

2007-04-07 15:56:53 · 9 answers · asked by carol s 2

Here is the question:

The coil of a galvanometer has a resistance of 20.0 ohms, and its meter deflects full scale when a current of 6.20 mA (mili-amperes) passes through it. To make the galvanometer into an ammeter, a 24.8 m-omhs (mili-ohms) shunt resistor is added to it. What is the maximum current that this ammeter can read?

The back of the book gives the answer as 5.01 amperes, but I am not sure how they obtained this result. It would be very helpful if someone could work this problem out step-by-step and show me how to do this type of problem.

2007-04-07 14:09:25 · 3 answers · asked by Ryan_1770 1

A tuning fork vibrating at 600 Hz is immersed in a tank of water, and the resulting sound waves in the water are found to have a wavelength of 8.2 ft. What is the velocity of sound in the water?

2007-04-07 13:59:12 · 3 answers · asked by Anonymous

2007-04-07 12:55:48 · 4 answers · asked by STORMY K 3

If the dc base current of a transistor with an hFE of 51 is 87 mA, then the approximate value of re’ is ________ohms

2007-04-07 12:25:05 · 1 answers · asked by sam19090 1

In nuclear fission, a nucleus of uranium -238, which contains 92 protons, divides into smaller spheres, each having 46 protons and a raduis of 5.9 x 10^-15 m. What is the net force on this pair of molecules?

using
kq1q2/r2
i got
(8.99 x 10^9) (46*(1.6x10^-19))^2
----------------------- -----------------------
(2*(5.9x10^-15))^2

= 3.47 x 10^23 N

2007-04-07 11:42:13 · 5 answers · asked by ARE JAY 1

Having difficulty answering this question, any help would be nice.

2007-04-07 11:40:55 · 4 answers · asked by Intuition 3

& how is electricity converted to heat for cooking?

Also if there are any websites that have the answer, the would be greatly appreciated.

2007-04-07 10:14:27 · 6 answers · asked by Anonymous

So last night I was at a woods party for my friends birthday. we're all sitting around a campfire and someone I know made the claim that if you throw a cinderblock into the fire, the cinderblock will actually blow itself apart and send chunks flying a few feet away after a few minutes in the fire.

I don't think it will but he claims to have seen it before firsthand, and several others agreed with him. I don't think it's likely but hell, ya never do know.


unfortunately we didn't happen to have a cinderblock handy to test it out.

2007-04-07 10:12:16 · 8 answers · asked by Anonymous

Slightly technical and pedantic question.
But, i was wondering, if things like Guage Bosons tell particles "what to do" (if you like) when they are exchanged and the hypothetical Higgs boson is supposed to be what gives matter a mass, then i was just wondering what could tell Space-time to curve around mass?

2007-04-07 10:07:19 · 5 answers · asked by Anonymous

An apple weighs . When you hang it from the end of a long spring of force constant and negligible mass, it bounces up and down in SHM. If you stop the bouncing and let the apple swing from side to side through a small angle, the frequency of this simple pendulum is half the bounce frequency. (Because the angle is small, the back and forth swings do not cause any appreciable change in the length of the spring.)

What is the unstretched length of the spring (i.e., without the apple attached)?


Ive gone through it all 3 times with silghtly different approaches.
I got

L = 4w/k

every time, but that is not correct. I am not sure what I am doing wrong..

Omega_bounce = sqrt(k/m) = 2*pi*f_bounce….solved for frequency of bounce.

f_pendulum = (1/2) f_bounce …. Solved for f_pendulum

omega_pendulum = 2*pi*f_pendulum = sqrt(g / L)….solved for L

Any Suggestions?

2007-04-07 10:01:42 · 2 answers · asked by Audrey B 1

A ring of mass 8 kg and radius 4 cm and cylinder of mass 3 kg and radius 2 cm are placed beside each other at the top of an inclined ramp. They are both released at the same time and roll without slipping down the ramp. Which object (ring or cylinder) reaches the bottom first?


a)they reach the bottom at the same time
b)ring reaches the bottom first
c)cylinder reaches the bottom first
d)insufficient information to determine

2007-04-07 09:38:11 · 1 answers · asked by Anonymous

twice as much as the other. The time to reach the ground will be
a. twice as long for the heavy ball
b. twice as long for the light ball
c. about the same for both
d. considerably longer for the light ball but not necessarily twice as long
e. considerably longer for the heavy ball

2007-04-07 07:52:26 · 12 answers · asked by boboboboboboboboo 2

ur friend, you standing 1 [m] apart from each other. If fahv (5)% of elecrtons in ur body moved to buddy, find electical force of attraktion betweeen ur buddy and u in lbs.

2007-04-07 07:19:58 · 1 answers · asked by Jonathan J 1