@harish3h • 28 Nov, 2010

Can anyone help me out in explaining why transformers are considered as passive circuits. Transformers performs by stepping up/down voltage/current,changes low input power to high output and vice versa.

But these are the basic definitions of an active device.A transistor also does this.Then why is transformer called a passive device?

Plz help me fellows?

@chandujntu • 28 Nov, 2010 Active components are those that have gain or directionality... Transformers simply convert one voltage level to another . but are not related with any gain terms. In case of transistors we have both gain and directionality features... Hence, transistors are active devices while transformers are passive..
@ISHAN TOPRE • 28 Nov, 2010 Harish3h,
A passive device is one which do not use its power or charge i.e; any active component for working of devices.In case of transformers it is the no.of turns of winding which is constant is used to merely step up or down voltage or current.
The magnetic flux is linked with the coils due to current flowing through the coil and nothing more.Hence Transformer is a passive device.
@narayana murthy • 29 Nov, 2010 not only these frequency also plays role in transformer as it is ac device so u can also concentrate on frequency i think it may be not the exact ans for ur question but it may help u so iam posting anyway if i found ans i will post again
@harish3h • 30 Nov, 2010 Thank u guys.. i'm enlightened
@nsiva007 • 30 Nov, 2010
Transformers performs by stepping up/down voltage/current,changes low input power to high output and vice versa.
In a transformer the input power and output power are the same....! i.e, V1xI1 = V2xI2,thus you get V1/V2 =I2/I1.... this is transformer ration...! By the way an Active element is the one that produces a Voltage or Current.... i.e a potential source or current source ,battery etc..! Transformer doesn't produce any power voltage or current...! hence its not an active component in a circuit...!
@Kavya Burramolla • 04 Feb, 2020 • 1 like

Transformer is a passive device the reason being when it is excited with the supply voltage it either step up or step down or produces the same voltage at the output end depending up on the application. But it will not have the ability to control the flow of electrical charge. Whereas active devices can control the flow of electrical charge. 

@Durgesh Srivastava • 20 Feb, 2020

The magnetic flux is linked with the coils due to current flowing through the coil and nothing more. Hence Transformer is a passive device. Transformers performs by stepping up/down voltage/current,changes low input power to high output. Whereas active devices can control the flow of electrical charge.

@Venkat Sai Nakkina • 08 Mar, 2020

In a transformer the input power and output power are the same. An Active element is the one that produces Voltage or Current. Transformer doesn't produce any power voltage or current. Hence Transformer is not an active device it is a passive device.

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