An electric circuit provides a closed path for the flow of current. Consider the circuit above, in which a lamp is connected to a battery through a resistor R. when the switch is closed, current flows through the lamp causing it to emit light. This is an example of electric circuits.
Electric circuit can also be defined as the pictorial or mathematical representation of the interconnection of physical components that constitute the flow of current. Every physical electrical component that we see around as has their own symbolic representation. An electric circuit is a method of representing the interconnection these components in a simpler form making it easy to analyse and design.
A circuit is said to be open when it does not provide a closed path for the flow of current. The circuit the switch is not closed or the circuit is damaged such that it could not provide a closed path for the flow of electric current.
A circuit is said to be closed when it can provide a closed path for the flow of current.
In a DC circuit, a short circuit is said to occur when the positive terminal comes in contact with the negative terminal or the ground. A short circuit may damage the whole equipment or one or more active or passive devices in the circuit.