Question

表一是某電熱水壺的銘牌；表二是小紅探究該電熱水壺效率所記錄的數(shù)據(jù)。

表一：                                 表二：

電源電壓U電/V 220 壺內(nèi)水的質(zhì)量m/ kg 1 水的初溫t1/℃ 33 水的沸點t2/℃ 98 水從初溫加熱至剛沸騰的時間t/s 250

產(chǎn)品型號 SWF12P1A—150 額定電壓U/V 220 電源頻率f/Hz 50 額定功率P/W 1200 容量V/L 1.2

求：（1）電熱水壺的電阻。

（2）當(dāng)電熱水壺實際工作電壓為110V時，它的實際功率。

（3）電熱水壺的效率。[c_水=4.2×10³J/（kg·℃）]

Answer 1

 （1）····································································· 1分

···························································· 1分

································································· 1分

      

 （2）解法一：

       ··························································· 1分

······················································ 1分

··································································· 1分

解法二：

       3分

_（3）

······························································ 1分

··········································································· 1 分