[{"data":1,"prerenderedAt":73},["ShallowReactive",2],{"q-fire-111-1-fire-science-018":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-111-1-火災學概要-018","fire-111-1-fire-science-018",111,1,18,"下列何者非電線走火之原因？",{"A":16,"B":17,"C":18,"D":19},"過負載","短路","接觸不良","接地","D",null,[],false,"本題考點：電線走火（配線起火）的成因分類，考的是把「保護措施」與「故障原因」分開。\n【正解理由】電線走火係指配線本身因異常發熱或放電而起火，常見成因包括電流超過安全電流量的過負載、線間絕緣破壞而電流暴增的短路、端子鬆動或素線斷裂造成的接觸不良，以及積污導電、金原現象等絕緣劣化。接地則是把設備外殼或系統中性點以導體連接大地的安全措施，目的在於使故障電流獲得低阻抗路徑導入大地，促使漏電斷路器或過電流保護裝置動作而切斷電源，本身並非導致導體異常發熱起火的原因，故選 D。\n【逐項排除】\n(A) 過負載使導體電流長時間超過安全電流量，焦耳熱累積導致絕緣劣化甚至起火，是走火原因。\n(B) 短路時線路阻抗趨近於零，瞬間大電流伴隨電弧與高溫熔痕，是最典型的走火原因。\n(C) 接觸不良使接點電阻升高而局部發熱，並可能反覆產生微小火花，是走火原因。\n(D) 接地為防止感電、促使保護裝置動作的安全設計，屬防制手段而非故障成因，為本題應選者。\n【記憶點】過負載、短路、接觸不良是「病因」，接地是「藥」，別把藥當成病因。","逐一拆解各成因的物理機制，這一題就不必死背。過負載的核心是焦耳熱，導體發熱功率等於電流平方乘以電阻，電流加倍發熱即成四倍；當負載長時間超過導線的安全電流量，絕緣被持續烘烤而軟化、龜裂，最後線間絕緣失效轉為短路。延長線捲繞成盤使用時散熱條件變差，是同一機制的加重版。\n短路是線間絕緣破壞後電流不經負載直接回流，阻抗趨近於零使瞬間電流達到數百甚至數千安培，接觸點產生電弧，電弧溫度可達數千度，足以熔化銅導體並噴濺熔珠引燃周邊可燃物。火災調查上會依熔痕的金相組織判別為起火原因的一次熔痕，或火勢延燒後才形成的二次熔痕。\n接觸不良指端子鬆動、氧化或多股導線逐條斷裂（半斷線），使接點的接觸電阻異常升高，電流通過時局部發熱，並在微小間隙間反覆放電，長期作用下可使接點附近的絕緣體碳化，與金原現象接軌。銅導體在此類接點反覆受熱氧化時，表面生成的氧化亞銅具有導電性且電阻高於銅，會使發熱更集中而不斷增厚，形成愈熱愈發熱的正回饋，是插座、開關端子起火的典型型態。\n接地的角色則完全不同：它是刻意設置的低阻抗故障電流路徑，使漏電時電流迅速回流而觸發保護裝置跳脫，並將金屬外殼電位維持在接近大地電位以防止感電。真正會引起火災的是「漏電」——電流經由非預期路徑（潮濕木材、金屬構件）流動而在高電阻處發熱，火災調查上須同時查明漏電點、出火點與接地點三要素才能認定。把接地與漏電混為一談，正是本題設計的陷阱。延伸考點包括無熔絲開關與漏電斷路器的功能差異、安全電流量與配線口徑的關係，以及電氣火災中熔痕、半斷線痕與碳化痕的鑑識意義。",true,[28,32,36,40,44,48],{"webId":29,"stem":30,"number":31,"year":11,"session":12},"fire-111-1-fire-science-017","有關閃燃（Flashover）與複燃（Backdraft）的敘述，何者錯誤？",17,{"webId":33,"stem":34,"number":35,"year":11,"session":12},"fire-111-1-fire-science-019","有關火羽流及天花板噴射流的敘述，下列何者錯誤？",19,{"webId":37,"stem":38,"number":39,"year":11,"session":12},"fire-111-1-fire-science-016","比較積污導電與金原現象之差異，下列何者錯誤？",16,{"webId":41,"stem":42,"number":43,"year":11,"session":12},"fire-111-1-fire-science-020","下列對於燃燒要素的敘述，何者錯誤？",20,{"webId":45,"stem":46,"number":47,"year":11,"session":12},"fire-111-1-fire-science-015","下列發火源在理化現象歸類上，何者與其他不同類別？",15,{"webId":49,"stem":50,"number":51,"year":11,"session":12},"fire-111-1-fire-science-021","下列有關熱量傳遞的敘述，何者正確？",21,[53,57,61,65,69],{"webId":54,"year":55,"stem":56,"number":13},"fire-113-1-fire-science-018",113,"空氣中氧氣的體積含量約為 X%，當氧濃度下降至 Y%時，一般燃燒難以持續，則 X，Y 分別為多少？",{"webId":58,"year":59,"stem":60,"number":13},"fire-112-1-fire-science-018",112,"若硝化纖維之化學式為 C24H32O12(NO3)8，則其硝化度為多少%？",{"webId":62,"year":63,"stem":64,"number":13},"fire-110-1-fire-science-018",110,"根據「危害物質災害現場搶救標準作業程序」之規定，其首要工作為何？",{"webId":66,"year":67,"stem":68,"number":13},"fire-109-1-fire-science-018",109,"化學災害搶救程序 HAZMAT 之說明，下列何者正確？",{"webId":70,"year":71,"stem":72,"number":13},"fire-108-1-fire-science-018",108,"當氣體進行「壓縮比=2」的斷熱壓縮時，下列對該氣體的敘述何者正確？",1785129966791]