Electric Current and Its Sources

Two or more cells are connected together to form a _____.

Can you think of any four devices which can work even when not connected to the switchboards at your home?

What is the total potential difference between them?

Explain what is electricity?

A cell of $\mathrm{e}\mathrm{m}\mathrm{f}\mathrm{ }E$ and internal resistance $r$ is connected in series with an external resistance $nr$ . Then, the ratio of the terminal potential difference to $\mathrm{e}\mathrm{m}\mathrm{f}$ is $\frac{n}{n+\alpha }$. Write the value of $\alpha$.

A circuit contains two cells one is primary and the other one is secondary. Both primary cell and secondary cell are rechargable.

What is the special property of a secondary cell? Give an example of the secondary cell.

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:

What is the frequency of alternating current in India?

Secondary cells can not be recharged.

Primary cells can not be recharged.

What are primary cells? Give an example also.

What are secondary cells? Give an example also.

Direction of current is taken opposite to the direction of flow of

Conventionally, the direction of the current is taken as

An electric cell has _____ terminals.

What is an electric cell?

Which one of the following  alternating current is supplied in our house hold circuits?

The device used for producing electric current is called :

Differentiate between AC current and DC current with the merits and demerits of AC current.

Discuss the difference between conventional current flow and electron flow.