Question

For the given circuit, comment on the type of transformer used.

A. Step-down transformer
B. Auxiliary transformer
C. Step-up transformer
D. Autotransformer

Answer 1

Hint: It is important to know about the transformer and its types. It is a device that transfers the electric energy from one AC circuit to one or more other AC circuits, either increasing or decreasing the voltage. Basically, there are two types of transformers : step-up transformer and step-down transformer. By considering this, let's answer the question.

Complete step by step solution:

Image: A transformer

The step-up transformer is one that increases the voltage from the primary winding to the secondary winding, thereby increasing the output voltage i.e., $$V_0>V_i$$. Similarly, the step-down transformer is one that decreases the voltage from the primary winding to the secondary winding, thereby decreasing the output voltage i.e., $$V_0<V_i$$.

In the question, they have given that the input voltage given to the transformer as $$V_i=220V$$, the output power as $$P_0=60W$$, the load current $$i_L=0.11A$$. Now, in order to find which type of transformer it is we need to find whether $$V_0>V_i$$ or $$V_0<V_i$$.
The formula for the power is given as,
$$P=V\times I$$
By the second circuit, we can write it as,
$$P_0=V_0\times I_0$$
Here they have given the value of $$P_0$$ and $$I_0$$...........($$I_0=I_L$$)

Rearranging the above equation for $$V_0$$ we get,
$$V_0={\displaystyle \frac{P_0}{I_0}}$$
$$\Rightarrow V_0={\displaystyle \frac{60}{0.11}}$$
$$\therefore V_0=545.45V$$
Now we can compare the values of $$V_0$$ and $$V_i$$ that, the input voltage,$$V_i=220V$$ and the output voltage, $$V_0=545.45V$$. Therefore, $$V_0>V_i$$ which concludes that it is a step-up transformer.

Hence, Option C is the correct answer.

Note:Transformers are used in the power transmission of electric energy. The step-up and step-down transformers depend on the windings of the primary and secondary coil and the transformer’s turn ratio.