| Topic: |
Science > Physics |
| User: |
"lucianb" |
| Date: |
11 Apr 2004 10:15:27 AM |
| Object: |
Help With Physics Problems!!!! |
Can anyone help me solving these problems:
1. A tension of 5V is measured between the ends of a wire. What was
the work done by the electric field while a charge of 100C was
passing through a cross-section of a wire? What is the resistance of
the wire if the current flow lasted for 23 seconds?
2. The pressure reqired for the water system of a town consisting of
four-storey buildings is that of a 24 m high water colunm. What is
the daily consumption of electric energy used for the water system of
a town with a popolation of 50000 if we count with a daily average of
100l per capita and if the efficiency of the pumps is 80% whereas
that of the electric motors is 92%.
3. Concrete blocks, each having a mass of 2.4tons, must be transfered
to a height of 16m and one block must be lifted every half minute.
The voltage of the elevator motor is 220V; its efficiency is 90%.
a) what is the power of the motor while lifting a block?
b) What is its current consumption during this time?
c) What is the electric energy used for the lifting of one block?
d) What does the electric elnergy used for lifting of one block cost?
(the price of 1kWh is 1.20Ft)
4. An aluminium wire and a copper wire, both of the same lenght, are
connected in series to a battery. Equal amounts of heat are generated
in them in equal times. what is the ratio between the cross sectional
areas of the two wires?
5. We connect an incandescent lamp designed for a power of 24 W and a
voltage of 12 V to a bettery having an internal resistance of 8 ohm.
The voltage drop across the lamp has just the required value!
a) What is the electromotive force of the battery?
b) What is the efficiency of the circuit?
6. We want to operate a 12V/15W lamp at its normal power, but we only
have a battery of an electromotive force of 24V and an internal
resistance of 3 ohm.
What should be the resistance of the resistor connected
a)in parallel
b)in series
with the lamp to ensure the desired operation
What is the efficiency of operation in each case?
7. When a pocket battery is short-circuited by a very thick copper
wire, the battery gets considerably warmer whereas the copper wire
remains cool. Why?
8. Which is the more economic way for transporting electric energy:
the one using high voltage or the one using low voltage? Give a
detailed explanation.
Thanks
.
|
|
| User: "lucianb" |
|
| Title: re:Help With Physics Problems!!!! |
11 Apr 2004 04:05:24 PM |
|
|
I can send u pics of women as many as u want :D but can u solve them
because i really need them to be done till thursday!!
Thanks,
Lucian
.
|
|
|
| User: "Greg Neill" |
|
| Title: Re: re:Help With Physics Problems!!!! |
11 Apr 2004 05:06:53 PM |
|
|
"lucianb" <lucian_baiesan@yahoo-dot-com.no-spam.invalid> wrote in message
news:4079b314$1_1@127.0.0.1...
I can send u pics of women as many as u want :D but can u solve them
because i really need them to be done till thursday!!
Post what you've done to try to solve the problems,
up to where you get stuck. People will help you
if you first show genuine effort. Who are you going
to ask when you're sitting your exams?
There's no Royal Road to knowledge, and it's uphill
most of the way.
.
|
|
|
|
|
| User: "Gregory L. Hansen" |
|
| Title: Re: Help With Physics Problems!!!! |
12 Apr 2004 10:22:38 AM |
|
|
In article <4079610f_1@127.0.0.1>,
lucianb <lucian_baiesan@yahoo-dot-com.no-spam.invalid> wrote:
Can anyone help me solving these problems:
Apply basic definitions in your textbook.
1. A tension of 5V is measured between the ends of a wire. What was
the work done by the electric field while a charge of 100C was
passing through a cross-section of a wire? What is the resistance of
the wire if the current flow lasted for 23 seconds?
W = Q delta V
I = dQ / dt
2. The pressure reqired for the water system of a town consisting of
four-storey buildings is that of a 24 m high water colunm. What is
the daily consumption of electric energy used for the water system of
a town with a popolation of 50000 if we count with a daily average of
100l per capita and if the efficiency of the pumps is 80% whereas
that of the electric motors is 92%.
50000 people use 100 L each per day. What is the total mass of that
water?
W = m g h
efficiency = 0.80 * 0.92
3. Concrete blocks, each having a mass of 2.4tons, must be transfered
to a height of 16m and one block must be lifted every half minute.
The voltage of the elevator motor is 220V; its efficiency is 90%.
a) what is the power of the motor while lifting a block?
P e = delta E / delta t
delta E = m g delta h
b) What is its current consumption during this time?
P e = I V
c) What is the electric energy used for the lifting of one block?
W = mgh
d) What does the electric elnergy used for lifting of one block cost?
(the price of 1kWh is 1.20Ft)
4. An aluminium wire and a copper wire, both of the same lenght, are
connected in series to a battery. Equal amounts of heat are generated
in them in equal times. what is the ratio between the cross sectional
areas of the two wires?
P = IV, V = IR, R ~ Length/Area
5. We connect an incandescent lamp designed for a power of 24 W and a
voltage of 12 V to a bettery having an internal resistance of 8 ohm.
The voltage drop across the lamp has just the required value!
a) What is the electromotive force of the battery?
P = IV, V = IR, current is the same at all points in a series circuit, the
voltage supplied by the battery is the sum of the voltages dropped across
the internal resistance and the lamp. The voltage drop across the lamp
has the required value, which means 12 V, and sufficient current to
produce 24 W.
b) What is the efficiency of the circuit?
P_lamp / P_internal
6. We want to operate a 12V/15W lamp at its normal power, but we only
have a battery of an electromotive force of 24V and an internal
resistance of 3 ohm.
What should be the resistance of the resistor connected
V = 12 V, P = IV
a)in parallel
1/R = 1/R1 + 1/R2
b)in series
R = R1 + R2
with the lamp to ensure the desired operation
What is the efficiency of operation in each case?
7. When a pocket battery is short-circuited by a very thick copper
wire, the battery gets considerably warmer whereas the copper wire
remains cool. Why?
P = IV, V = IR
8. Which is the more economic way for transporting electric energy:
the one using high voltage or the one using low voltage? Give a
detailed explanation.
P = IV, V = IR
--
"Are those morons getting dumber or just louder?" -- Mayor Quimby
.
|
|
|
|
| User: "The Ghost In The Machine" |
|
| Title: Re: Help With Physics Problems!!!! |
11 Apr 2004 04:52:43 PM |
|
|
In sci.physics, lucianb
<lucian_baiesan@yahoo-dot-com.no-spam.invalid>
wrote
on 11 Apr 2004 10:15:27 -0500
<4079610f_1@127.0.0.1>:
Can anyone help me solving these problems:
When is the homework due? :-)
1. A tension of 5V
"Tension"? Interesting word choice.
is measured between the ends of a wire. What was
the work done by the electric field while a charge of 100C was
passing through a cross-section of a wire? What is the resistance of
the wire if the current flow lasted for 23 seconds?
What is an amp? What is a watt? Answer those questions and you're
well on your way.
2. The pressure reqired for the water system of a town consisting of
four-storey buildings is that of a 24 m high water colunm. What is
the daily consumption of electric energy used for the water system of
a town with a popolation of 50000 if we count with a daily average of
100l per capita and if the efficiency of the pumps is 80% whereas
that of the electric motors is 92%.
If an item is, say, 85% efficient, then for every 100 joules put into
the item, 85 comes out as usable work. g = 9.805 m/s/s, the density
of water is 1 metric tonne per cubic meter, or 1 kg per liter.
3. Concrete blocks, each having a mass of 2.4tons, must be transfered
to a height of 16m and one block must be lifted every half minute.
This translates into a power or wattage requirement..
The voltage of the elevator motor is 220V; its efficiency is 90%.
a) what is the power of the motor while lifting a block?
Wattage requirement divided by efficiency.
b) What is its current consumption during this time?
E = VI.
c) What is the electric energy used for the lifting of one block?
A requirement for solving a). Note that this is different from
the *mechanical work* required, as the electric motor isn't 100%
efficient.
d) What does the electric elnergy used for lifting of one block cost?
(the price of 1kWh is 1.20Ft)
Not sure what a 'Ft' is, but I'm assuming it's a monetary unit.
One can either convert joules into kWh or simply compute the
number of blocks lifted per hour.
4. An aluminium wire and a copper wire, both of the same lenght, are
connected in series to a battery. Equal amounts of heat are generated
in them in equal times. what is the ratio between the cross sectional
areas of the two wires?
I'd have to look, but hopefully somewhere one has a description of
the resistance of aluminium and copper.
5. We connect an incandescent lamp designed for a power of 24 W and a
voltage of 12 V to a bettery having an internal resistance of 8 ohm.
The voltage drop across the lamp has just the required value!
a) What is the electromotive force of the battery?
b) What is the efficiency of the circuit?
c) What is the resistance of the lamp? V = IR, P = VI = I^2R = V^2/R.
6. We want to operate a 12V/15W lamp at its normal power, but we only
have a battery of an electromotive force of 24V and an internal
resistance of 3 ohm.
What should be the resistance of the resistor connected
a)in parallel
b)in series
with the lamp to ensure the desired operation
What is the efficiency of operation in each case?
7. When a pocket battery is short-circuited by a very thick copper
wire, the battery gets considerably warmer whereas the copper wire
remains cool. Why?
Three guesses.
8. Which is the more economic way for transporting electric energy:
the one using high voltage or the one using low voltage? Give a
detailed explanation.
What is the power dissipated by a wire, given the voltage?
Thanks
--
#191,
It's still legal to go .sigless.
.
|
|
|
|
| User: "lucianb" |
|
| Title: re:Help With Physics Problems!!!! |
12 Apr 2004 09:26:53 AM |
|
|
To be frank i just looked over the problems and i didn't have a idea
how to start. that's y i posted them on the forums. I'll be online in
the next 4hours so if anyone could give me a hand it would be great.
does anyone have yahoo messenger (or msn) - my nick is lucianfx (i'm
online now - on yahoo). We can solve them much faster there!.
Thanks.
Ps: I need them done for Thu. I'm really desperate! :(
.
|
|
|
| User: "Greg Neill" |
|
| Title: Re: re:Help With Physics Problems!!!! |
12 Apr 2004 10:56:32 AM |
|
|
"lucianb" <lucian_baiesan@yahoo-dot-com.no-spam.invalid> wrote in message
news:407aa72d$1_2@127.0.0.1...
To be frank i just looked over the problems and i didn't have a idea
how to start.
In other words, you haven't even bothered to open
your course textbook? Have you attended any classes?
If you'd done either, you should have some inkling as
to how to get started on at least *some* of the
questions.
that's y i posted them on the forums. I'll be online in
the next 4hours so if anyone could give me a hand it would be great.
does anyone have yahoo messenger (or msn) - my nick is lucianfx (i'm
online now - on yahoo). We can solve them much faster there!.
Thanks.
Ps: I need them done for Thu. I'm really desperate! :(
I am reminded by an old saying: "A lack of planning on
your part does not constitute an emergency on my part."
.
|
|
|
|
| User: "Sam Wormley" |
|
| Title: Re: Help With Physics Problems!!!! |
12 Apr 2004 09:31:15 AM |
|
|
lucianb wrote:
To be frank i just looked over the problems and i didn't have a idea
how to start. that's y i posted them on the forums. I'll be online in
the next 4hours so if anyone could give me a hand it would be great.
does anyone have yahoo messenger (or msn) - my nick is lucianfx (i'm
online now - on yahoo). We can solve them much faster there!.
Thanks.
Ps: I need them done for Thu. I'm really desperate! :(
Dear desperate
Suggestion: spend the time with your textbook and exercising your
brain.
.
|
|
|
|
|
| User: "Ian Stirling" |
|
| Title: Re: Help With Physics Problems!!!! |
11 Apr 2004 12:02:11 PM |
|
|
lucianb <lucian_baiesan@yahoo-dot-com.no-spam.invalid> wrote:
Can anyone help me solving these problems:
How much are you willing to pay for the answers.
Naked pictures of attractive female relatives may be acceptible.
Can you at least show your attempts?
1. A tension of 5V is measured between the ends of a wire. What was
the work done by the electric field while a charge of 100C was
passing through a cross-section of a wire? What is the resistance of
the wire if the current flow lasted for 23 seconds?
2. The pressure reqired for the water system of a town consisting of
four-storey buildings is that of a 24 m high water colunm. What is
the daily consumption of electric energy used for the water system of
a town with a popolation of 50000 if we count with a daily average of
100l per capita and if the efficiency of the pumps is 80% whereas
that of the electric motors is 92%.
3. Concrete blocks, each having a mass of 2.4tons, must be transfered
to a height of 16m and one block must be lifted every half minute.
The voltage of the elevator motor is 220V; its efficiency is 90%.
a) what is the power of the motor while lifting a block?
b) What is its current consumption during this time?
c) What is the electric energy used for the lifting of one block?
d) What does the electric elnergy used for lifting of one block cost?
(the price of 1kWh is 1.20Ft)
4. An aluminium wire and a copper wire, both of the same lenght, are
connected in series to a battery. Equal amounts of heat are generated
in them in equal times. what is the ratio between the cross sectional
areas of the two wires?
5. We connect an incandescent lamp designed for a power of 24 W and a
voltage of 12 V to a bettery having an internal resistance of 8 ohm.
The voltage drop across the lamp has just the required value!
a) What is the electromotive force of the battery?
b) What is the efficiency of the circuit?
6. We want to operate a 12V/15W lamp at its normal power, but we only
have a battery of an electromotive force of 24V and an internal
resistance of 3 ohm.
What should be the resistance of the resistor connected
a)in parallel
b)in series
with the lamp to ensure the desired operation
What is the efficiency of operation in each case?
7. When a pocket battery is short-circuited by a very thick copper
wire, the battery gets considerably warmer whereas the copper wire
remains cool. Why?
8. Which is the more economic way for transporting electric energy:
the one using high voltage or the one using low voltage? Give a
detailed explanation.
Thanks
.
|
|
|
|
|
Related Articles |
|
|
