A storage battery of emf 8.0 V and internal resistance 0.5Ω is being charged by a 120 V dc supply using a series resistor of 15.5Ω. What is the terminal voltage of the battery during charging? What is the purpose of having a series resistor in the charging circuit?

The current lags behind the voltage by a phase different of $\pi /2$ radian, when in the circuit is:

A cell of negligible resistance and emf $2$ volt is connected to a series combination of $2, 3$ and $5$ ohm. The potential difference in volts between the terminals of $3$-ohm resistance will be:

চিত্রে একটি বৈদ্যুতিক বর্তনী দেখানো হল।

A capacitor (C$=40\mu$F) is connected through a resistor ($R=2.5$M$\Omega$) across a battery of negligible internal resistance of voltage $12$ volts. The time after which the potential difference across the capacitor becomes three times to that of resistor is (ln $2=0.693$).