20Ω表示：该滑动变阻器的最大阻值为20欧姆
或6400imp/kwh
“220V10A”
10A表示:该电能表连续工作时允许通过的最大电流为10安培
重要的物理公式
| 序号 | 定义式 | 变形公式 | 各物理量及单位 | |||||
| 1 | ρ＝m/V | V=m/ρ m=ρV | ρ密度 | kg/m3 | m质量 | kg | V体积 | m3 |
| g/cm3 | g | cm3 | ||||||
| 2 | v=s/t | s=vt t=s/v | v速度 | m/s | s路程 | m | t时间 | s |
| km/h | km | h | ||||||
| 3 | P= W/t | W=Pt t=W/P | P功率 | w | W功 | J | t时间 | s |
| kw | Kw·h | h | ||||||
| 4 | G =mg | m = G/g | G重力/ N | m质量/kg | g=9.8N/kg | |||
| 5 | F浮=G排 =ρ液gV排 | ρ液 = F浮/g V排 | F浮 浮力/N | ρ液体密度kg/m3 | V排排开液体体积/m3 | |||
| V排 = F浮/ρ液g | ||||||||
| 6 | p= F/S | F =pS S = F/p | p压强/Pa | F压力/N | S受力面积/m2 | |||
| 7 | W = Fs | F = W/s s = W/F | W功/J | F力/N | s做功的距离/m | |||
| 8 | η= W有/W总 | W有 =ηW总 | W总=W有/η | η效率 | W有 有用功/J | W总总功/J | ||
| 9 | W总=W有+ W额 | W有= W总-W额 | W总总功/J | W有 有用功/J | W额 额外功/J | |||
| 10 | W = UI t | U= W /I t t = W/ UI | W电功/ J | U电压/V | t时间/s | I电流/ A | ||
| 11 | I = U/R | U = RI R = U/I | I电流/A | U电压/V | R电阻Ω | |||
| 12 | W = n/N | N = n/ W n = N W | n电表转数/r | W电能/ Kw·h | N电能表常数/r/ Kw·h | |||
| 13 | P = W/t =UI | U = P/I I = P/U | P电功率/W | U电压/V | I电流/A | |||
| 14 | Q放=I2Rt | R = Q放/I2t t= Q放/I2R I2 = Q放/ Rt | Q 电热/ J | I电流/ A | R电阻/ Ω | t时间/s | ||
| 15 | Q放 = mq | m = Q放/q q = Q放/m | Q热量/J | m 质量/ kg | q热值 J/kg J/ m3 | |||
| 16 | Q = cmΔt | Δt = Q/cm m = Q/cΔt c = Q/mΔt | Q 热量/J | c 比热容 J/(kg ℃) | m质量/kg推荐阅读
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