Class 7 Science Chapter 10 Notes Electric Current and its Effects
→ Battery : It is 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.
→ Electrical components : Electric components are basic devices which connects together to make an electric circuit. 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.
→ Electric cell : It is a device which is used to generate electricity. It has two terminals.They are positive and negative terminals.
→ Electromagnet : The magnet made by using an electric current is called electromagnet. It consists of coil of insulated wire wrapped around a piece of iron that is magnetised only when electric current is passed through the coil.
→ Fuse : A fuse is a safety device that protects electrical circuits from the effects of excessive currents.
→ Hearing effect of current : When a wire get hot when an electric current passes through it is called 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.
→ An electric circuit consists of electric cell or battery, electric wires, switch and bulb.
→ Electric components and their symbols are :
→ Symbolic representation of an electric circuit with its components is known as circuit diagram.
→ Flow of electric charges through a closed circuit is known as electric current. It flows from the positive terminal to the negative terminal of a cell in the circuit. Also, it flows from a higher potential to lower potential.
→ A group of two or more cells forms a battery.
Arrangement of cells :
→ A switch is used to control the flow of electricity in a circuit.
→ A bulb glows when electric current passes through its filament. Its filament is made up of tungsten.
→ Current flowing in a wire can produce heat and this is known as the heating effect of current.
→ The amount of heat produced by current depends upon the
- nature of the material of object
- the amount of current flow
- the amount of time for which current flows.
→ The heating effect of current is utilized in the heating devices like electric iron, kettle, geyser, toaster, etc.
→ The coils of heating devices are made of nichrome.
→ Materials like tungsten and nichrome have the ability to withstand high temperatures, without melting.
→ A fuse is a safety device for electrical circuits and appliances, based on heating effect of current. It is a thin small wire made of tin or an alloy of tin and copper whose melting point is low.
→ The function of a fuse is to break a circuit, in case there is overheating due to shortcircuiting or overloading.
Miniature Circuit Breakers (MCBs) are now widely used instead of fuses. These are switches which automatically turn off when current in a circuit exceeds the safe limit.
→ A current flowing in a wire can produce a magnetic field around the wire. This is known as the magnetic effect of electric current.
→ The property of electric current is used to change magnetic materials like soft iron into magnets by passing electricity through them, such magnets are called electromagnets.
→ An electromagnet loses its magnetism as soon as the electric current is switched off. Thus, it is a temporary magnet.
→ The strength of electromagnet is directly proportional to the amount of current flowing through coil and the number of turns of the coil. It is inversely proportional to the length of the coil.
→ Solenoid is a device in which a long insulated wire is wound around a hollow inetallic core. A current- carlying solenoid behaves like a bar magnet.
→ An electric bell also uses an electromagnet.
