current and resistance

我在此向大家請教:

1.是不是一定要有electric current才會有resistance? Why?

2. There are three series circuits and each of them is connected with an ammeter.

Close all circuits. The readings of the ammeter are 0A, 0.5A and 1.5A respectively.

Which of the circuit has a lowest value of resistance? Why?

Thx!!!

1 個解答

評分
  • 天同
    Lv 7
    1 十年前
    最愛解答

    1. Of course not. "Resistance" is a physical property of a substance, just like mass or volume. The resistance of a substance always exists irrespective there is current passing through it or not.

    2. Provided that voltages applied to the three circuits are the same, the one with lowest resistance will draw the largest current from the source. This follows Ohm's Law. Hence, the circuit with 1.5A current has the lowest resistance.

    Mathematically, if V is the applied voltage to the circuit, then the current I flowing through it is given by,

    I = V/R (Ohm's Law)

    or R = V/I

    For the three circuits, the respective resistances R1, R2 and R3 are thus,

    R1 = V/0 (this indicates infinite resistance, or open circuit)

    R2 = V/0.5 = 2V

    R3 = V/1.5 = 2V/3

    Clearly, the value of R3 is the lowest.

    • Commenter avatar登入以回覆解答
還有問題嗎?立即提問即可得到解答。