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Reviewed CSCA Physics question · Easy

两个电阻 R1 = 6 Ω 和 R2 = 3 Ω 串联后接在电压为18 V的电源两端，求 R1 两端的电压。

  1. 6 V
  2. 9 V
  3. 12 V
  4. 18 V
Show the answer and explanation

Correct answer

C. 12 V

Principle or equation

串联电路电流处处相等，总电阻 R = R1 + R2，电流 I = U / R，分压 U1 = I R1。

Why this answer is correct

总电阻 R = 6 + 3 = 9 Ω，电流 I = 18 / 9 = 2 A，U1 = 2 * 6 = 12 V。

Example

若 R1=4Ω，R2=2Ω，电压12V，则 U1 = 12/(4+2)*4 = 8V。

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