CBSE Class 7 Science Chapter 14 Notes Electric Current and Its Effects
Electric Current and Its Effects Class 7 Notes Understanding the Lesson
1. Electricity is an important source of energy in our day-to-day life.
2. An electric cell is a device which is used to generate electricity.
3. An electric cell has two terminals:
- positive terminal
- negative terminal.
4. A combination of two or more cells in which the positive terminal of one cell is connected to the negative terminal of the next cell, is called a battery (Fig. 1).
5. An electric circuit is an arrangement of different components such as the electric cell, battery, switch, electric bulb and wire. It is the complete path from one terminal of the electric cell through the bulb and back to the other terminal of the electric cell.
6. It is convenient to represent electric components by symbols. Using these, an electric circuit can be represented by a circuit diagram.
7. When an electric current flows through a wire, the wire gets heated. It is the heating effect of current.
8. In the bulb there is a thin wire called the filament, which glows when an electric current passes through it, due to heating effect of current.
9. Other appliances where the heating effect of the current is used are electric iron, heater, immersion heaters, geysers, hairdryers, etc.
10. The amount of heat produced in a wire depends upon its material, length and thickness.
11. Wires made from special materials melt quickly and break when large electric currents are passed through them. These wires are used for making electric fuses.
12. When electric current passes through a wire, it behaves, like a magnet. This is the magnetic effect of the electric current. In fact, electric current can be used to make magnets.
13. An electromagnet is an example of the magnetic effect of the electric current. It is used in many devices like electric bell, loudspeakers, telephone, etc.
14. An electric bell mainly consists of an electromagnet, a hammer and a gong.
15. We should conserve energy today to avoid energy crisis later.
Class 7 Science Chapter 14 Notes Important Terms
Battery: Battery is a combination of two or more cells in which the positive terminal of one cell is always joined to the negative terminal of other cell.
Electrical components: Electric components are basic devices which connect together to make an electric circuit. For example, switch, battery, bulb, etc.
Circuit diagram: A circuit diagram is a graphical representation of an electric circuit which is drawn using symbols of different electrical components.
Cell holders: Cell holders are two or more compartments which hold the cells to make a battery. Cells are placed in them properly, such that the positive terminal of one cell is connected to the negative terminal of the next cell.
Filament: Filament is a thin wire in the bulb which glows when an electric current passes through it.
Element: The coil of wire in an electric room heater or an electric heater is called an element.
Electric fuses: An electric fuse is a safety device which prevents damages to electric circuits and possible fires. It is made from some special materials which melt quickly when large electric currents are passed through them.
Heating effect of current: When a wire get hot when an electric current passes through it, is called the heating effect of current.
Magnetic effect of current: When an electric current passes through a wire, it behaves like a magnet. This is called the magnetic effect of current.
Electromagnet: The magnet made by using an electric current is called electromagnet. It consists of a coil of insulated wire wrapped around a piece of iron that is magnetized only when electric current is passed through the coil.
Electric bell: An electric bell is a device based on magnetic effect of current. It consists of an electromagnet, a hammer and a gong.