Biology; Chemistry; Physics: Post your doubts here!

[Rimsa]

because the cable is insulated? if not our house would no electricity when raining?

ahan' this is an mcq. i need a reason from these four...

 

[ashiqbal]

Hey guys....need help in these questions fast: ashiqbal SalmanPakRocks

1. w11 qp_21 Question 3 (a) (i)

2. s11 qp_22 Question 5 (a)

3. s10 qp_22 Question 11 (a)

4. w10 qp_22 Question 9 (a)

5. w09 qp_2 Question 11 (c) (i)

THanks in advance...please please reply as soon as possible

1. you have to draw thermocouple like this : (very badly drawn)
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2.
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3.it is a very long diagram, you have to draw a labelled piece of wire, a cell, and ammeter in series. and a voltmeter connected in parallel to wire. then you have to draw a thermocouple with one end touching wire and other in water at 0 degrees. finally add some heating source to wire, eg heat over flame, heat in oven, etc, just to show how temp is changing. then plot V against I to obtain different values of resistance
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4.
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5. we will find change in V with temperature to calibrate the V scale. then we will use the X or the small piece of metal to notice change in V which we can use to find temperature

 

[ashiqbal]

my explaination rejected?

which one? didnt see sorry , must have passed! can u please send again?

 

[ashiqbal]

why can birds stand on overhead transmission lines without suffering any harm?
-their bodies are of high resistance?
-good insulator feet
-no potential difference b/w feet
- spaces b/w feathers act as insulators..
which one? shouldnt the reason be that they arent connected to earth so thats why? :s

my guess would be C = -no potential difference b/w feet, which is the same as your guess because they arent connected to earth, so no current flows and no p.d!

 

[Rimsa]

my guess would be C = -no potential difference b/w feet, which is the same as your guess because they arent connected to earth, so no current flows and no p.d!

thanks

 

[ashiqbal]

my explaination rejected?

because it wan upward force? mean the answer is resultant + Weight? if just resultant the rocket is unable to move? too heavy?

ok got it now!

 

[luckywang]

Describe the operation of Transformer...

when the current is switch on, a magnetic field is produced in the coil, the produced magnetic field first produced is big enough to cut the coil on the other side off the transformer so a current is induced in the other side of the coil... so AC power supply is required is provide the 'first big magnetic field' can keep produce to cut the coil on the other side...
this thing is think by myself... didnt verify with teacher coz my friend say it is correct and i use this concept on every school exam... hope is the correct one...
correct if got any error...

 

[ashiqbal]

when the current is switch on, a magnetic field is produced in the coil, the produced magnetic field first produced is big enough to cut the coil on the other side off the transformer so a current is induced in the other side of the coil... so AC power supply is required is provide the 'first big magnetic field' can keep produce to cut the coil on the other side...
this thing is think by myself... didnt verify with teacher coz my friend say it is correct and i use this concept on every school exam... hope is the correct one...
correct if got any error...

the concept is ok, though the language needs a bit revising, it gets a bit muddled up in the middle, No offense!

 

[luckywang]

the concept is ok, though the language needs a bit revising, it gets a bit muddled up in the middle, No offense!

help me to correct it?

 

[ashiqbal]

Describe the operation of Transformer...

help me to correct it?

when an AC current flows through the coil around a ring of soft magnetic material such as iron, it produces a magnetic flux because of the constantly changing direction of current. this magnetic flux is carried around in the iron ring to the output wires, where the reverse occurs and a changing magnetic field produces an AC current. by changing the number of turns in the input and output coils, we can vary the voltage according to our needs.

 

[Dukeofwin]

Where do v use them!!!

We use step down when we send the high voltage from power stations to our homes that require low voltage.
And step up is used in Electricity Stabilizers which increase the low voltage to normal required one

 

[snowbrood]

why do current flow through all branches in parallel circuit?? why isnt there a short circuit? anyone to help me​

 

[Dukeofwin]

why can birds stand on overhead transmission lines without suffering any harm?
-their bodies are of high resistance?
-good insulator feet
-no potential difference b/w feet
- spaces b/w feathers act as insulators..
which one? shouldnt the reason be that they arent connected to earth so thats why? :s

Last option!

 

[Rimsa]

Last option!

umm ashiqbal said C.

 

[ashiqbal]

We use step down when we send the high voltage from power stations to our homes that require low voltage.
And step up is used in Electricity Stabilizers which increase the low voltage to normal required one

kia keh rahy ho? step up is used when transmitting the power from power stations to our homes!
step down is used to convert back the high voltage to low voltage so that it can be used in our homes!

 

[luckywang]

why do current flow through all branches in parallel circuit?? why isnt there a short circuit? anyone to help me​

every branches got a load? if got, no short circuit will occur! eg. got two branches, one got resistor and one got nothing... then the clever current will choose the easiest way to pass so a short circuit will happen!

 

[ashiqbal]

umm ashiqbal said C.

i am sure it is C! spaces between feathers do act as insulator, but for heat, and that is not related to electricity!

 

[luckywang]

kia keh rahy ho? step up is used when transmitting the power from power stations to our homes!
step down is used to convert back the high voltage to low voltage so that it can be used in our homes!

absolutely right!

 

[Rimsa]

i am sure it is C! spaces between feathers do act as insulator, but for heat, and that is not related to electricity!

i see. okay thanks

 

[Dukeofwin]

kia keh rahy ho? step up is used when transmitting the power from power stations to our homes!
step down is used to convert back the high voltage to low voltage so that it can be used in our homes!

Nope! I cant be wrong on this one! Voltage is decreased when sent to our homes only 220-240 volts out of 22000 or something! Thus its a step down!