[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-110-1-fire-science-027":3},{"subject":4,"subjectSlug":5,"subjectKicker":6,"subjectShort":7,"question":8,"related":27,"sameNumber":52,"hasEssay":26},"火災學概要","fire-science","火災學 · Fire Science","火災學",{"id":9,"webId":10,"year":11,"session":12,"subject":4,"number":13,"stem":14,"options":15,"answer":20,"answerNote":21,"images":22,"imagesPending":23,"lawTimestamp":11,"explanation":24,"explanationDeep":25,"freq":12,"indexable":26},"fire-110-1-火災學概要-027","fire-110-1-fire-science-027",110,1,27,"某建築物的插座電壓為 110 伏特，在其延長線上的插座同時插 880 瓦的電磁爐、110 瓦的電風扇及 1100 瓦的電熱器，請問該延長線之額定電流至少需多少安培？",{"A":16,"B":17,"C":18,"D":19},"209","110","19","9","C",null,[],false,"本題考點：電功率、電壓與電流的關係式 P = I × V,以及延長線額定電流不足所形成的過載情境。\n【正解理由】家用插座為單相交流，電熱類電器可視為電阻性負載，功率關係為 P = I × V,故 I = P ÷ V。三項電器同時使用時總功率為 880 W + 110 W + 1100 W = 2090 W,在 110 V 下所需電流為 2090 W ÷ 110 V = 19 A。延長線的額定電流必須不小於實際負載電流，因此至少須 19 A,故選 C。常見家用延長線額定多為 10 A 或 15 A,本題負載已超出，即屬典型的過載。\n【逐項排除】\n(A) 209 A:係將 2090 W 誤除以 10 而得，或把電壓當成 10 V,量級與家用迴路明顯不符。\n(B) 110 A:直接抄用電壓數值 110,單位張冠李戴，伏特不等於安培。\n(C) 19 A:2090 W ÷ 110 V 的正確結果，正確。\n(D) 9 A:僅計入電磁爐 880 W 與電風扇 110 W(合計 990 W ÷ 110 V = 9 A),漏算 1100 W 的電熱器。\n【記憶點】瓦數先相加再除以電壓;110 V 迴路下，大約每 110 W 就是 1 A。","過載起火的機制可由焦耳定律說明：導線本身有電阻 R,通電後的發熱量 P = I²R,發熱與電流的平方成正比。電流增為 2 倍，發熱量即為 4 倍。當實際電流超過導線的容許電流，產生的熱量無法藉由散熱平衡，溫度持續累積，先使聚氯乙烯(PVC)被覆軟化、碳化，絕緣性能劣化後導致短路或積污導電，終致起火。線徑越細、串接越長，電阻越大、發熱越明顯，這是延長線比固定配線更容易出事的原因。\n\n電氣火災的成因在火災調查上通常分為幾類：過載(本題情境)、短路(含層間短路與金屬熔痕)、接觸不良(插頭鬆動產生電弧與局部高溫)、積污導電(插座間積聚灰塵與濕氣，沿表面形成碳化導電路徑，俗稱插座起火)、半斷線(導線部分股線斷裂，剩餘截面電流密度暴增)、以及漏電。命題常把本題的算式與這些成因合併考，先算電流再問屬於何種成因。\n\n另可延伸比較電壓的影響：同一 2090 W 負載改以 220 V 供電時，電流降為 9.5 A,發熱量僅約四分之一，這正是大功率電器多採 220 V 專用迴路的理論依據。此外，無熔絲開關與保險絲的額定值必須配合導線的容許電流，若額定值選得比導線容許電流高，過載時開關不會跳脫，保護即形同虛設——這也是常見的判斷題陷阱。\n\n計算上還須區分視在功率與實功率：電動機、日光燈這類含電感的負載功率因數小於 1,實際電流為 P ÷(V × cosθ),會大於單純以 P ÷ V 求得之值；本題三項屬電熱器具與小型電風扇，以電阻性負載處理即可。若題目改為以電動機為主的負載而仍忽略功率因數，算出的電流就會偏低。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-110-1-fire-science-026","易燃性氣體受到壓縮後溫度會有升高的狀況發生，可能會發火導致火災的發生，此現象為何？",26,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-110-1-fire-science-028","下列有關電器用品「焦耳熱」之敘述，何者錯誤？",28,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-110-1-fire-science-025","請依據可燃性氣體完全燃燒時的化學理論濃度，計算丙烷的燃燒下限？",25,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-110-1-fire-science-029","工廠使用之乙炔（C2H2），為防止爆炸引起火災，常利用裝有某化學物質與多孔性物質充填物之鋼瓶加壓保存，請問該化學物質為何？",29,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-110-1-fire-science-024","在充足的能量下，下列何種濃度（vol%）的氫氣（H2）為燃燒界限範圍內？",24,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-110-1-fire-science-030","某建築物火場產生大量煙霧，正向煙囪效應在中性帶以上 10 公尺處的壓力差為 12 Pa，若建築物內、外的溫度差不變，請問中性帶以上 20 公尺處的壓力差為何？",30,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-027",113,"火災發生後至閃燃發生的時間稱為閃燃時間（F.O.T.），影響閃燃時間的重要因素，下列何者錯誤？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-027",112,"下列何種措施於室內發生火災時有助於防止或延緩閃燃的發生？",{"webId":62,"year":63,"stem":64,"number":13},"fire-111-1-fire-science-027",111,"下列關於乙炔的敘述，何者錯誤？",{"webId":66,"year":67,"stem":68,"number":13},"fire-109-1-fire-science-027",109,"下列有關泡沫滅火劑，何者敘述正確？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-027",108,"有關粉塵的最小發火能量，下列敘述何者正確？",1785129967094]