[amp_mcq option1=”0.25″ option2=”180″ option3=”0.5″ option4=”4 E. None of the above” correct=”option1″]
The correct answer is $\boxed{4}$.
The impedance ratio of a transformer is the ratio of the secondary impedance to the primary impedance. It is a dimensionless quantity and is denoted by the symbol $k$.
The impedance ratio can be calculated using the following formula:
$$k = \frac{Z_s}{Z_p}$$
where $Z_s$ is the secondary impedance and $Z_p$ is the primary impedance.
In this case, the primary impedance is $60 \Omega$ and the secondary impedance is $120 \Omega$. Therefore, the impedance ratio is:
$$k = \frac{Z_s}{Z_p} = \frac{120 \Omega}{60 \Omega} = 4$$
Option A is incorrect because $0.25$ is not the impedance ratio of a transformer.
Option B is incorrect because $180$ is not the impedance ratio of a transformer.
Option C is incorrect because $0.5$ is not the impedance ratio of a transformer.
Option D is incorrect because $4$ is the impedance ratio of a transformer.