Given,

• Potential difference in primary coil \( \rm V_{A} = 220 V \)
• Number of turns in primary coil \( \rm N_{A} = ? \)
• Potential difference in secondary coil \( \rm V_{B} = 440 V \)
• Number of turns in secondary coil \( \rm N_{B} = 350 \)

a) In a transformer, the potential difference is directly proportional to the number of turns in the coil. \[ V \propto N \]

Using formula,

\( \rm \frac{V_{A}}{V_{B}} = \frac{N_{A}}{N_{B}} \)

\( \rm or, N_{A} = \frac{V_{A}}{V_{B}} \cdot N_{B} \)

\( \rm or, N_{A} = \frac{220}{440} \cdot 350 \)

\( \rm \therefore N_{A} = 175 \)

Hence, there are 175 turns in the primary coil of the transformer.

b) If the coil of the transformer is not laminated, eddy current develops in it. This results in a loss of energy in the form of heat. It decreases the efficiency of the transformer.

c) No, it cannot be used by connecting to a battery because a transformer works with an Alternating Current. However, a battery is a source of Direct Current.