Heater係用高resistance定係低resistance

Heater係用高resistance定係低resistance(連解釋)

3 個解答

評分
  • tc
    Lv 6
    1 十年前
    最愛解答

    決定 heater 的 resistance ,要考慮兩個因素:

    powerefficiency在理想的情況下,根據 P = V²/R,Heater 的 resistance 越少,power 越大,越能夠迅速加熱,所以 heater 的 resistance 會比其他家電低。

    但是,實際上,resistance 並非越低越好,因為電路中的電線、電源及heater電路中的其他部份都會有 restistance (R2),如果 heater 的 resistance (R1) 太低,R1 的 p.d. 會變少,R2 的 p.d. 會變得大,很多電力會浪費在 R2 ,甚至可能令 R2 過熱,所以 heater 的 resistance 要低,但比整個電路的其它電阻高。

    一般學生都錯誤以為 heater 的 resistance 要高,因為他們知道電流流過電阻會生熱,便以為電阻越大,產生的熱量會越大。無錯,電流流過電阻會生熱,但是若電阻增加,電流會減少 (因為 V = IR),所釋放出來的熱能也會減少 (P = I² R)。

  • 天同
    Lv 7
    1 十年前

    It should be low resistance.

    The heating effect of a heater is due to the current that flows through the heating element. A lower resistance permits a higher current to pass through, thus producing more heat.

    Examples, a 1000W heater connected to the domestic mains of 220 V would have a resistance of,

    using power = voltage^2/resistance

    or resistance = voltage^2 /power = 220^2/1000 Ohms = 48 Ohms

    A 500W heater will have a resistance of

    resistance = 220^2/500 Ohms = 97 Ohms

    Hence, a higher power heater should have a lower resistance.

  • 1 十年前

    Of course high resistance.

    Heat is given out when electrons pass through a high resistance area.

    As heater is use to give out heat, an ideal heater should have high resistance.

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