變壓器 Watt & mA ?

Question

1) 為何有些 變壓器 的標示內容: out put 150mA 為單位; 有些為out put 10watt 為單位?

2) 若在out put DC 7..5V ~ 150mA 即等於多少 Watt?

Answer 1

最愛解答

1. These are only different presentation of the same physical qunatity, the output power of the transformer.

The output voltage of a transformer is definitely known, hence given the ouptut current, the output power can be worked out. The direct giving of the current instead of power facilitates the estimation of charging time of batteries, which is ususally given in mAh.

2. Power = voltage x current = 7.5 x 150/1000 watts = 1.125 watts

Answer 2

Something you have to know:

P=IV

it means Current(I) x Voltage(V) = Power(Watt)

1)

為何有些 變壓器 的標示內容: out put 150mA 為單位; 有些為out put 10watt 為單位?

it doesn't really matter at all.

I suppose the output voltage is DC10V,

output 150mA(0.15A)xDC10V = 1.5W

10Watt output / DC10V = max 1A,

2)

若在out put DC 7..5V ~ 150mA 即等於多少 Watt?

according to P=IV

DC7.5V x 0.15A(150mA) = 1.125W