家庭电路由进户线→电能表→总开关→保险装置→用电器/插座组成。
火线 (L)和零线 (N)之间的电压为 220V。火线与大地之间电压也是 220V，零线与大地之间电压为 0V。
用电器之间是并联关系——每盏灯或插座独立工作，互不影响。开关要接在火线上。
进户线中还有地线 (PE)——连接用电器金属外壳和大地，防止漏电触电。
Household circuits: service entrance → meter → main switch → fuse/breaker → appliances/outlets.
Live (L) and neutral (N): 220V between them. Live-to-earth: 220V. Neutral-to-earth: 0V.
Appliances are connected in parallel — each works independently. Switches must be on the live wire.
A ground/earth wire (PE) connects metal appliance casings to earth, preventing shock from leakage.
如果开关接在零线上,即使断开开关,用电器仍然带电,维修时可能触电!
测电笔: 用来分辨火线和零线。笔尖接触导线,手指接触笔尾金属体。如果氖管发光,说明是火线。
保险丝: 用电阻率大、熔点低的铅锑合金制成。当电流过大时,保险丝发热熔断,自动切断电路保护用电器。
空气开关: 现代家庭常用,跳闸后可复位,使用更方便。
保险丝不能用铜丝/铁丝代替——它们熔点太高,电流过大时不会熔断,起不到保护作用!
Test pen: Distinguishes live vs. neutral. Touch tip to wire, finger on metal cap. Neon glow = live wire.
Fuse: Made of lead-antimony alloy (high resistivity, low melting point). When current is too high, the fuse melts and breaks the circuit to protect appliances.
Circuit breaker: Common in modern homes, resettable after tripping.
Never replace a fuse with copper/iron wire — their melting point is too high; they won't melt under overcurrent!
人体的安全电压是不高于36V。家庭电路220V远超安全电压,绝对不能触碰裸露导线!
触电原因: 人体直接或间接接触火线,与大地或零线形成回路,有电流通过人体。
常见触电形式:
①单线触电: 一只手接触火线,脚站在地上
②双线触电: 两只手分别接触火线和零线(更危险!)
③跨步电压: 高压线落地后,两脚之间有电压差
Electric shock cause: Body directly or indirectly contacts the live wire, forming a circuit with earth or neutral.
Common forms:
①Single-line: one hand touches live, feet on ground
②Double-line: each hand touches live and neutral (more dangerous!)
③Step voltage: near fallen high-voltage lines
• 不接触低压带电体（如裸露导线）
• 不靠近高压带电体（如变压器、高压线）
• 不用湿手触摸电器、开关
• 不超负荷用电（大功率电器不同时使用）
• 发现有人触电: 先断开电源,再进行急救
• 电器着火: 先切断电源,不能用水泼
第一步: 立即切断电源（拉闸或用干燥木棍挑开电线）。绝不能用手直接拉触电者!
第二步: 如果触电者已失去意识但有心跳呼吸,使其平躺,保持呼吸道通畅。
第三步: 如果触电者心跳或呼吸停止,立即进行心肺复苏(CPR)并拨打120急救电话。
Step 1: Cut power immediately (pull breaker or use dry wooden stick to move wire). Never touch the victim directly!
Step 2: If unconscious but breathing, lay the person flat, keep airway open.
Step 3: If heartbeat or breathing stops, start CPR and call emergency services.