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Thermal Physics

Blazing goIITian

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3 Mar 2009 12:49:34 IST

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Q. 4 At some temperature T, a bronze pin is a little too large to fit into a hole drilled in a stee

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Q. 4 At some temperature T, a bronze pin is a little too large to fit into a hole drilled in a steel block. The change in temperature required for an exact fit is minimum when 1. only steel block is heated 2. only bronze pin is cooled 3. both block and pin are heated 4. both block and pin are cooled

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saharsha kumar keshkar

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3 Mar 2009 15:54:58 IST

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see the figure ,if u heat the exapinsion will take place and both r1 and r2 will increase.....

hence according u r question...

ans (a)-only steel block is heated ....seems to correct...

nudge me if i m wrong.

CHEERS!

JPS

Blazing goIITian

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3 Mar 2009 20:10:15 IST

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but how can u say that change in temperature required is min. in dis case????

Feuer Zaber

Blazing goIITian

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3 Mar 2009 20:44:58 IST

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No I dont think so.I think it will expand both ways rather than just R2 increasing.

Its better to cool whichever one that has a larger alpha value so that change in size is easier.

saharsha kumar keshkar

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3 Mar 2009 21:12:46 IST

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ya vinu is correct......

i was bit confused in ques tion...

let me think again.......but visnu seems to be correct.

JPS

Blazing goIITian

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4 Mar 2009 00:10:17 IST

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someone else reply...........

AViK

Blazing goIITian

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4 Mar 2009 14:25:02 IST

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Statistics say the expansion coeff. of Steel > expansion coeff. Bronze....

Tht means for per unit increase in temp. Steel expands more than Bronze...& fr per unit decrease in temp. Steel contracts more than bronze...

(c) & (d) r obviously cancelled as if both heated pin will expand which v don't want & if both cooled hole will contract...

Hence option (a) heating steel block ..shud b correct...

saharsha kumar keshkar

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4 Mar 2009 20:16:31 IST

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avik!

thats the same answer which i m getting........

islahul

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7 Mar 2009 20:21:16 IST

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-my answer is 2.bronze has got higher coefficient of expansion.for positive output 1,2 are obvious and 4 is because of above reason.when both cooled bronze becomes smaller faster than steel...i am pretty confirm with the answer . for coefficient of expansion visit:http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.htmldo rate reply

islahul

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7 Mar 2009 20:22:20 IST

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well for the temperature change to be minimum answer if 2nd option.

Madmax

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7 Mar 2009 20:40:52 IST

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I agree with avik....even before reading the other answers, I came to the conclusion tht answer should be a) .....cheers!!

saharsha kumar keshkar

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9 Mar 2009 16:22:38 IST

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even my answer is (A).......

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