A transformer has a primary voltage of $3.0\,\text{V}$. Its secondary voltage is $5.0\,\text{V}$, and the secondary current is $2.0\,\text{A}$. The transformer operates at $100\%$ efficiency. What current flows in the primary side of the transformer?
- A$1.2\,\text{A}$
- B$2.0\,\text{A}$
- C$3.3\,\text{A}$
- D$7.5\,\text{A}$