標題:

此文章來自奇摩知識+如有不便請留言告知

electric circuit(CE pp)

發問:

http://img177.imageshack.us/img177/9629/electric3.jpg 36.B, when resistance decrease, current increase. Why resistance remains unchanged? And why voltage increase? 37.D 40.A, why (2)and(3) incorrect 46.A, especially st(3), explain this statement Thank you for your help!

最佳解答:

(36) The rated current Io = V/r where V is the rated voltage and r is the resistance of the appliance The actual current flowing is Io/2 = V/(R + r) V/2r = V/(R + r) => R = r When V is doubled to 2V, the current will become 2V/(R+r) = 2V/2r = V/r = Io so B is correct. (37) The Ammeter indicates the total current through R and also the voltmeter (although the current through the voltmeter is small) (40) When S is closed,, the R3 and A3 reduces to a short circuit. The equivalent resistance of the total circuit is reduced. Therefore the current through R1 and R2 will increase. The current through a resistance is the ratio of the voltage to resistance. The voltage across R1 (and A1) is the same as the voltage across R2 (and A2). I1 = V/R1, I2 = V/R2 therefore I1/I2 = R2/R1 will not change no matter S is closed or not. When S is closed, all current will be directed to the short circuit path, and no current will flow through A3. (46) Equivalent resistance for X is given by 110^2/Rx = 40 or Rx = 110^2/40 = 302.5 Ohm Equivalent resistance for Y is given by 110^2/Ry = 80 or Ry = 110^2/80 = 151.25 Ohm When connected to 220V, the power for X will be 220^2/302.5 = 160W When X and Y are in series, the equivalent resistance is 302.5+151.25 = 453.75 Ohm Current = 220/453.75 = 0.4848A Power consumption for X = 0.4848^2 * 302.5 = 71.1W Power consumption for Y = 0.4848^2 * 151.25 = 35.6W

其他解答:FAD2A23AB937987B

arrow
arrow
    文章標籤
    章魚丸 我想 左幾耐 江湖 警察
    全站熱搜
    創作者介紹
    創作者 dvhtlbz 的頭像
    dvhtlbz

    dvhtlbz的部落格

    dvhtlbz 發表在 痞客邦 留言(0) 人氣()

    E-mail轉寄