A current that always flows through an electric device in the same direction is called  direct current or $\mathrm{DC}$. The polarity (positive and negative) of a direct current is fixed.

A current that reverses direction at equal intervals of time is called the alternating current or $\mathrm{AC}$. The polarity (positive and negative) of an alternating current is not fixed.

Both $\mathrm{DC}$ and $\mathrm{AC}$ can be used for lighting and heating. Some electric devices like the television need $\mathrm{DC}$ to operate. In such cases, an adapter or a device is fitted into them to convert $\mathrm{AC}$ from the mains supply to $\mathrm{DC}$.

On the basis of above information, answer the following:

The household supply that we get reverses its direction every

A current that always flows through an electric device in the same direction is called  direct current or $\mathrm{DC}$. The polarity (positive and negative) of a direct current is fixed.

A current that reverses direction at equal intervals of time is called the alternating current or $\mathrm{AC}$. The polarity (positive and negative) of an alternating current is not fixed.

Both $\mathrm{DC}$ and $\mathrm{AC}$ can be used for lighting and heating. Some electric devices like the television need $\mathrm{DC}$ to operate. In such cases, an adapter or a device is fitted into them to convert $\mathrm{AC}$ from the mains supply to $\mathrm{DC}$.

On the basis of above information, answer the following:

For long distance transmission of electricity, which one is generally preferred?

Match the items in Column I to those in Column II.

Note: Option (c) changed from potential difference between neutral and earth wires in a domestic circuit in volts to works on heating effect of current.