有一电源,当外电阻是14欧姆,测得端电压为2.8v,当外电阻为2v,测得端电压为2v?
三、3、
设电动势为E,电源内阻为 r;
E * 14/( 14 + r ) = 2.8,14E = 2.8 * 14 + 2.8 r;①
E * 2/( 2 + r ) = 2,E = 2 + r;②
② 代入 ①,28 + 14r = 2.8 * 14 + 2.8 r,r = 1 Ω;
E = 2 + r = 2 + 1 = 3v 。
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三、3、
设电动势为E,电源内阻为 r;
E * 14/( 14 + r ) = 2.8,14E = 2.8 * 14 + 2.8 r;①
E * 2/( 2 + r ) = 2,E = 2 + r;②
② 代入 ①,28 + 14r = 2.8 * 14 + 2.8 r,r = 1 Ω;
E = 2 + r = 2 + 1 = 3v 。