主要区别–交流和直流电源

连接到交流和直流电路的元件会消耗电力。术语“交流电源”和“直流电源”是指在这两种不同类型的电路中消耗的功率。在基本层面上，两种电路中的功率计算都使用相同的概念。然而，由于交流电路中电流的方向总是变化的，所以损耗的功率也会周期性地变化。交流和直流电源的主要区别在于，在直流电路中，耗散的功率保持不变，而在交流电路中，耗散的功率周期性地变化。

什么是直流电源(dc power)？

DC current refers to a current formed by electr*** flowing continuously in one direction. As the electr*** flow through various components in the circuit, they lose their electrical energy. DC power refers to the amount of energy  dissipated per second by a coulomb of electr***, as they travel between two points in a circuit. In a DC circuit, if a component has a potential difference  across it and a current  flowing through it, and if the component’s resistance is  , then the power dissipated by the component is given by:

如果直流电流是稳定的，那么组件消耗的功率也几乎是恒定的（我们假设影响功率消耗的温度和其他物理因素不变）。大多数日常部件，包括**和个人电脑，都使用直流电来工作。

什么是交流电源(ac power)？

AC current refers to currents formed by electr*** moving back and forth, set up by a terminal that has an oscillating voltage. During the cycle of back-forth motion, electr*** periodically speed up, slow down, and come to a momentary stop. Therefore, the current is also changing periodically. The instantaneous power  refers to the amount of power dissipated between two points in the circuit/by a component at any given time. It is given by:

where  and  are the potential difference and current at that time.

However, because and are always changing, instantaneous power is also c***tantly changing. The average power is a much more useful concept for components connected to AC circuits. When the time taken to complete a full oscillation by electr*** (i.e. their period) is given by , average power can be calculated as:

Suppose potential difference  across the component varies sinusoidally, and that the current lags behind the voltage by a phase angle  . Then we can show that the average power can be given by:

Here,  and refer to the root mean square values of voltage and current respectively, i.e. when the maximum voltage achieved during voltage change is  and the maximum current is  , then:

and 

下图显示了在电流滞后于电压30度的交流电路中，瞬时功率如何随电位差和电流而变化。虚线突出显示了平均功率。

Variation of voltage, power and current in an AC circuit

请注意，瞬时功率为负时，时间间隔很小。这是因为在这个电路中，在这个时间间隔内，能量被送入电源。这是因为电路中有一个感性负载，它可以抵抗电流的任何变化。这就是电流首先落后于电压的原因。

交流电(ac)和直流电源(dc power)的区别

权力的价值

在直流电路中，通过元件耗散的功率保持不变（理想情况下）。

在交流电路中，通过元件耗散的功率不断变化。

负载能量损失

在直流电路中，功耗只发生在一个方向上。i、 e.负载会不断地将能量从电路中释放出来并进入周围环境。

在交流电路中，电容/电感负载可以抵抗电流的变化，因此它们有时可以向电路中注入能量。