Electricity and Circuit

Dry Cell: A dry cell is usually made of metallic cylinder. It has a flat base and a metallic cap on top. The metallic cap on top is the positive (+) end of the cell. The flat base is the negative (-) end of the cell. A cell usually produces 1.5 V of current.

Electric Cell: Electric cell is a device which produces electric current because of chemical reaction. Electric cells can be of dry type or wet type. The car battery is made up of wet cells. The cells in a torch are dry cells.

Torch Bulb

Fig: Torch bulb

A torch bulb is made up of spherical glass which is attached to a metallic base. There is a filament inside the bulb. The filament is attached to two wires. One of the wires is attached to the metallic base of the bulb. Another wire is attached to the side of the metallic portion of the bulb. The side of the bulb is the negative pole, while the bottom is the positive pole.

Connecting the torch bulb to the cell: For this, you need to attach the wires to the two ends of the cell. The positive pole of the cell should be connected to the positive terminal of the bulb. Similarly, the negative pole of the cell should be connected to the negative terminal of the bulb.

Possible reasons for a torch bulb failing to glow:

• Connections may be loose.
• The bulb may be fused.
• The cell’s energy may be sapped.

Fig: Electric circuit

Electric Circuit

A closed path through which the electric current flows is called an electric circuit. The direction of electric current in an electric circuit is from the positive terminal to the negative terminal. This is opposite to the direction of flow of electrons; which is from the negative terminal to the positive terminal.

Electrical Switch: This is a device which helps in making or breaking an electric circuit. An electric switch allows us to use electric current as and when required. Switches are seen in many electrical devices and also in household wiring.

Fig: Structure of torch

Structure of Torch

A torch is made up of a cylindrical or cuboidal casing. The casing can be metallic or non-metallic. The cells are kept inside the casing. The bottom of the casing has a spring which is attached to the metallic wire. The spring helps in keeping the cells snugly fit in place. The metallic wire is attached to a switch. The switch is then attached to the negative terminal of the holder. The positive end of the holder touches the positive terminal of the cell at top. The bulb fits inside the holder.

Conductors: Materials which allow electric current to pass through them are called conductors. All metals are good conductors of electricity.

Insulators: Materials which do not allow electric current to pass through them are called insulators. Most of the non-metals are insulators, e.g. asbestos, rubber, wood, etc.