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Physics, Chemistry and Biology: Post your doubts here!

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i knw dat bt cn we use the crookes ratemeter exp for thx
Xylferion cn u ans ?

There's no need to go all complicated and include stuff like the radiometer. Instead there's a much simpler experiment than what either of you want to use.

Bring two surfaces, one black and the other white, close to a heat source. Attach a Coin to wax, and the wax to both surfaces.

The better absorber will melt the wax and the coin will fall, the poor absorber will absorb less heat and the coin will still stick to the wax.
 

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How to draw? I can't do it!!
View attachment 43131

The focal length is 3.0 cm. That means 3.0 cm from the centre of the lens. You draw this on both sides of XY, to the left and to the right. Then you label these points as F.

Next it says that your object is at the 2.0 cm mark to the left of the lens, mark this point, and draw an object 2.0 cm high.

Draw a line to XY from the top of your 2.0 cm line, and draw a line from the top of your 2.0 cm line, that intersects with the centre of line XY.

Extend both these lines and you will see an image form behind your object. This image is virtual and magnified.

Here's one tip I can give you, whenever your object is in between the lens and F. The image produced will always be virtual and magnified.
 
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For this, you should remember that if a body is dropped from a certain height, it's final velocity is given by v = acceleration due to gravity * time = gt.
So, to find time taken for stone to drop, since the stone takes the same time to drop as sound from the boat takes to reach the listener.
→ Time = Dist (btw boat and man)/ Speed (of sound)
t = 800/320 = 2.5s
Substituting in v = gt → v = 10 * 2.5 = 25 m/s

Hope you get it. :p
 
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oh, alright thanks :) then i lost at least 1 mark today...

wait!! current may flow, but the polarity may differ, and the reversed battery will be damaged.
Now three DC batteries/Sources are connected in series,while the one is of reverse polarity of the 2 others ( that cause to establish two currents with opposite direction of each other). Under such a series connection, the resultant voltage is measured by subtracting the lower voltage from the higher one. And finally direction of current can be determined after we calculate the resulting voltage.
 
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wait!! current may flow, but the polarity may differ, and the reversed battery will be damaged.
Now three DC batteries/Sources are connected in series,while the one is of reverse polarity of the 2 others ( that cause to establish two currents with opposite direction of each other). Under such a series connection, the resultant voltage is measured by subtracting the lower voltage from the higher one. And finally direction of current can be determined after we calculate the resulting voltage.
how cn the current flow , as it would act like a barrier and so break the circuit bt i guess there ll be a p.d across the batteries
 
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COULD? COULD?? You surprise me, Phoenix Blood
Begging your heart out for a leaked paper that's due tomorrow and mulling over whether it COULD be cheating? Carry on, everything's perfectly okay.
Shut you, understand? I'm not doing any sort of begging out here, nor did I have any intention of obtaining the paper. Keep your surprises to yourself- i don't need telling. Over.
 
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how cn the current flow , as it would act like a barrier and so break the circuit bt i guess there ll be a p.d across the batteries

P.D is the energy used to push th current, so if two current are pushing against each other, the one which has more volt will be able to push the other one (she mentiond 3 batteries, and one is reversed) so its 2:1, in small circuit i dont think there may be a large damage, so stronger current will flow but with less volts and the pole of the current may be reversed.
 
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