Electric Current & Its Effect
An electric cell is a device which converts chemical energy into electric energy.
The cell has two different metal plates – one is the positive terminal and the other is the negative terminal. These plates are kept inside a chemical called electrolyte. The cell is a source of electric current. Electric current is the flow of electrons or charge.
An electric circuit is the closed path along which electric current flows from the positive terminal to the negative terminal of the cell.
A circuit generally has:
(a) a source of electric current - a cell or battery.
(b) connecting wires for carrying current.
(c) a device which uses the electricity - a bulb etc.
(d) a key or a switch – This may be connected anywhere along the circuit to stop or allow the
flow of current
(A) Battery :
The positive terminal of one cell is connected to the negative terminal of the next cell. Such a combination of two or more cells is called a battery. Many devices such as torches, transistors, toys, TV remote controls, use batteries.
Connecting two cells together to make a battery
(B) Bulb :
In the bulb there is a thin wire, called the filament, which glows when an electric current passes through it. When the bulb gets fused, its filament is broken.
(C) Electric switch :
An electric switch is a device that opens or closes an electric circuit.
When the switch (key) K is closed, the circuit is complete; current flows through the circuit and the bulb glows.
When the switch (key) K is open, the circuit is not complete; current does not flow through the circuit and the bulb does not glow.
SYMBOLS OF ELECTRIC CIRCUIT
Some common electric components can be represented by symbols.