F.3 Physics specific heat Problem Urgent!!!

Question

Suppose the mass and temperature change of the aluminium block are m and T respectively, and the initial and final readings of the joulemeter are J1 and J2 respectively. Which of the following is true about the specific heat capacity of the aluminium block c? (Please give explanation either in Chinese or English)

A. c is greater than m x T x ( J2 - J1)

B. c is less than ( J2 - J1)/( m x T )

C. c is greater than ( J2 - J1 ) /( m x T)

D. c is greater than m x ( J2 - J1 ) / T

Answer 1

如果沒有heat lost to surrounding
E=mCT
J2-J1=mCT
C=(J2-J1)/(mXT)
如果考慮有heat lost，相同的(J2-J1)引至的溫度改變會較小，所以以較小的T代入上式所求出的C比真實數值為大。例如真實的溫度變化應該有10度但由於有熱能的散失，只升了9度，代入上式，除以9的結果當然大於除以10啦。
所以真正的C應該小於(J2-J1)/(mXT)
答案B是正確的。