Closed & Open Circuit

The Mission:

Students will be able to explain the closed and open electrical circuit. The students are expected to create a game in which they have to identify torches with fault in connection i.e. having open circuit and find the ratio of (i) Faulty torches to Properly working torch and (ii) Faulty torch to total number of torch produced.

2. Concepts to understand:

Introduction:

We are surrounded with electrical appliances all around us. These appliances run on electrical energy. The electrical energy which we get in the form of electricity is generated in power plants. With the use of electricity, our daily life is much simpler and easy. In our modern day, we use television, ceiling fans, lights and a lot many appliances which run on electricity. Without electricity we will be living in a dark age.

2.1 Electric Circuits:

The electricity that we get in our homes is used by appliances to do work, make our life easier etc. Every appliance has electric circuits inside it through which the electricity reaches the different components. Electricity flows in the form of electric current, which flows through wires made of specific materials. These materials are called as conductors. Conductors allows electric current to flow through them.

There are two main types of electric circuits:

1. Open Circuit
2. Closed Circuit

Before understanding what are open and close circuits, let us understand the different basic electrical components

• Components of electrical circuit

 A simple electrical circuit have different components. Every component plays a unique role in ensuring proper functioning of any electric circuit. Let us understand them one by one.

Electric Cell:

An electric cell is a component used to run electrical appliances. An electrical cell produces small amount of electrical energy to run small appliances. The electric cell produces energy through the chemicals stored inside the electric cell

Electric Bulb:

We all know what an electric bulb does, it gives light! Electric bulb is the most basic component of an electric circuit. When electricity is passed through the electric bulb, it gives out light and heat.

Light Emitting Diode:

A light emitting diode (LED) is an electric component which also gives out light energy. Light emitting diode is a semiconductor that gives out light similar to electric bulb. But LED’s consume less energy than a conventional electric bulb.

Wires:

Wires are components through which electric current reaches appliances. In our homes we have electric wiring surrounding us, these wirings are insulated because electric current is very dangerous. Electric current can cause electric shock in living beings upon contact. Hence electric wires are often insulated with materials like rubber, plastic etc. Inside a wire, it is made up of conducting metals like copper.

Resistors:

Resistors are components that are used in electrical circuits to reduce to flow of electric current. The reduction of electric current helps in regulating the current required for appliances to function optimally. The electrical appliances internally have built in resistors to only give a required amount of current to ensure the functioning of the electrical appliance

Switch:

A switch is a component which can cut off the supply of electric current through a simple on/off switch. A switch can either let the current pass through the circuit or completely cut it off. Switches play an important role through which we can either start or stop any appliance.

Electric Fuse:

A fuse is an electrical component that protects electrical appliances from excess current. At times, due to power surge, there is always a chance that the surge can cause damage to the appliances. An electric fuse gets damaged in turn and protects the electrical appliances. Electrical fuses are of different ratings that are used for different appliances.

2.3 Open and closed circuit.

Generally electric circuits are either closed or open. A closed electric circuit means that switch is in open state and the electric current is flowing in the electric circuit.

2.3.1 Closed Circuit:

When the circuit forms a closed loop with the switch in ON position, then the circuit is complete. A completely closed loop circuit is called as a closed circuit. In a closed circuit, connected with a battery and an appliance, electric current will flow through the circuit. A switch in an ON state in an electric circuit forms a closed circuit thus allowing electric current through flow in the circuit because of the battery. In this case the electric bulb will glow since the electric current is passing through the circuit and makes the bulb glow.

2.3.2 Open Circuit:

An open electric circuit implies that the electric circuit is not functioning and electric current is not passing through it. If electric current doesn’t pass through the circuit, then the appliance will not function. In this case it is an electric bulb that will not glow because the switch is in an OFF state.

2.3.3 Factors that can cause an open Circuit:

 An electric circuit could not be operational for the following reasons:

• When the components are not properly connected to each other
• If wire is broken in the electrical circuit
• If the bulb is fused (not working)
• If the fuse connected in the circuit breaks

Due to these reasons the path for the current breaks and the circuit becomes open. The figure below shows various configurations in which circuit may or may not be operational.

2.4 Tester to identify open and closed circuit.

A simple tester can be made using, a cell, three pieces of electric wire, a bulb connected as shown in the figure 4. Your tester is ready.

To test whether the circuit is open or closed, we just need to connect this tester around the components of the electrical circuit. When the switch is in the off position the circuit is open and the tester wont work.

Using the tester, each component of the circuit can be tested individually.

Use the tester in the following situations:

• To test whether the fuse in a circuit is broken or not, place wire A of the tester to one end of the fuse, and wire B of the tester to the other end of fuse. If bulb of tester glows then the fuse is working proper. If bulb does not glow, then fuse is broken. And we need to replace the fuse.
• To test whether the bulb is fused or not, place wire A of the tester to one terminal of the bulb, and the other wire B to the negative terminal of the bulb. If both the bulbs glow, then the bulb forms the circuit is working properly. If both the bulbs do not glow then the bulb from the circuit is fused and we need to change it.

To identify other components of the circuit, we need to place the terminals of those equipment between the open ends of wire A and B of the testers.

To check the components of a closed working circuit, the electric cell from the is removed. Only bulb with two connecting wires is used as a tester. The wires of this tester are connected across the components of the working electric circuit. If current pass through the tester, bulb will glow indicating that the circuit is working properly. For any faulty component of circuit the bulb would not glow.