Difference between Open Circuit and Short Circuit

A closed path following an electric current is known as an electric circuit or simply circuit. An electric circuit consists of a number of circuit components such as resistors, inductors, capacitors, etc.

Sometimes in an electric circuit, two undesirable conditions occur namely open circuit and short circuit. Basically, these two states of an electric circuit are considered as faults in the circuit and hence are undesirable. In this article, we will highlight the major differences between an open circuit and a short circuit.

What is an Open Circuit?

As its name suggests, an open is a break in the path of the current in the circuit. Therefore, an open circuit can be defined as a break or interruption in the circuit path.

An open circuit may be as a result of a component failure or disconnection of a conducting path such as breaking of a conducting wire.

For any electrical circuit, by Ohm’s law, we have,

$$\mathrm{R\:=\:\frac{V}{I}}$$

Now in case of open circuit, the current through the circuit is zero, thus,

$$\mathrm{R\:=\:\frac{V}{0}\:=\:\infty}$$

Hence, ideally an open circuit offers infinite resistance in the path of electric current.

The effect of open circuit in a series circuit and a parallel circuit is different. That is, in a series circuit following symptoms can be observed −

• The total circuit current becomes zero.

• There is no voltage drop across the components which are normal.

• The total supply voltage will appear across the open circuited terminals.

• The terminal voltage of source may measure higher than the normal.

Following are the effects of an open circuit in a parallel circuit −

• The total circuit will decrease.

• The current through the open circuit branch becomes zero, while the operation of the branches without open circuit will be normal.

What is a Short Circuit?

In any electrical circuit, the unwanted path of low resistance is called short circuit. When a short circuit occurs in an electric circuit, the total resistance of the circuit becomes very low.

Consequently, the total circuit current becomes greater than the normal which may cause damage of other heathy devices in the circuit.

The common reasons of occurrence of short circuit in an electric circuit are insulation failure, components get shorted, etc.

The effect of short circuit in both series circuits and parallel circuit is almost same. Sometimes, the short circuits are result in electric fire, explosion, etc.

Mathematically, by Ohm’s law, we have,

$$\mathrm{R\:=\:\frac{V}{I}}$$

When there is a short circuit in the circuit, the circuit current becomes infinitely high, thus,

$$\mathrm{R\:=\:\frac{V}{\infty}\:=\:0}$$

Hence, a short circuit ideally offers a resistance of zero ohms in the path of current.

Differences between Open Circuit and Short Circuit

Both open and short circuits are unwanted conditions in an electric circuit and are treated as a fault in the circuit. However, there are several differences between open and short circuit that are listed in the following table −

Basis of Difference	Open Circuit	Short Circuit
Definition	When there is a break in the conducting path of an electric circuit, it is called open circuit.	When there is an unwanted path of very low resistance in an electric circuit is called short circuit.
Resistance	The resistance of an open circuit is tending to infinity. Ideally, it is considered infinity.	The resistance of the short circuit is tending to zero, and ideally it is taken zero.
Circuit current	The current flowing through an open circuit is zero.	The current flowing through a short circuit is infinite.
Voltage	The voltage across the open circuit is equal to the voltage of the supply.	The voltage of a short circuit is ideally zero, because the resistance of an ideal short circuit is taken zero.
Causes	In practice the main causes of an open circuit are failure of device or component, breaking of the conducting wire, etc.	The causes of short circuit are insulation failure, shorting of component, etc.
Practical applications	Open circuit may also be used in a right way, as in case of an OFF switch.	Sometimes , the short circuits are also used in a useful way such as, to short the secondary winding of a current transformer during maintenance, etc.

Conclusion

The most significant difference between an open circuit and a closed circuit is that an open circuit has a resistance tending to infinite, whereas a short circuit has a resistance tending to zero.