The path of flow of electricity starting from one terminal of cell and returning to the other is called an electrical circuit. It consists of conducting wires and other resistances (like lamps etc.) between the terminals of a battery, along which an electric current flows.

(a)     Open Electric Circuit : An electric circuit through which no electric current flows is known as open electric circuit. The electric circuit will be open circuit if the plug of the key is taken out or if the connecting wires break from any point.

(b)     Closed Circuit : An electric circuit through which electric current flows continuously is known as closed circuit.


*    For flow of electricity, the circuit must be made of conductors. Insulators in the path of electrical circuits makes the circuit  incomplete.

Ex.3    Look at the circuit given in figure (a) and figure (b). Read the instructions in each case and answer the questions given.

I.    Which bulb B1/B2 in figure (a) will glow when 
    (a) only K1 is closed ?

   (b) K1 and K2 are closed ?

   (c) K1, K2 and K3 are closed ?    

   (d) only K2 and K3 are closed ?

Sol.    (a) No bulb will glow, (b) Bulb B1 will glow, (c) B1 and B2 both will glow and (d) No bulb will glow. 
II.        Which bulb B1/B2/B3 in figure (b) will glow when
        (a) only K1 is closed ?
        (b) only K2 is closed ?
        (c) both K1 and K2 both are closed ?    
Sol.    (a) Bulb B3 will glow, (b) No bulb will glow and (c) All  will glow.