Series and Parallel Connections at Home

Key Concepts

• Fuse
• MCB
• Tripping
• Live wire
• Neutral wire
• Grounding

Introduction: 

The wiring in our household is of different colors. They are red, black and green. Different appliances have different plugs. When a switch is loaded with multiple electrical appliances, the MCB trips and the electricity of the house goes out. In this session we are going to learn the reason behind this along with different kinds of electrical safety measures in our household for our safety. 

Explanation: 

Circuit breakers: 

Circuit breakers open the circuit when a current in a house wire exceeds the rated current for that circuit. It protects people from being electrocuted to death and from burning down the house.  

A few safety circuit breakers used at home are: 

• Fuse 
• MCB 

Fuse: 

A fuse is the simplest device, which breaks the circuit under abnormal conditions. It is used for overload or short circuit protection at high and low voltage. 

Electric fuse is based on the principle of heating effect of electric current. Heat is produced when current flows in the wire. When excess current flows through the wire, huge amount of heat is produced due to excessive flow of current. This heat melts the fuse, which normally has a low melting point, thereby preventing any damage to the electric circuit and appliances. 

Advantages:  

• Speed of operation is very high. 
• Maintenance costs are practically zero. 
• They can clear high as well as low current. 
• They provide reliable operation. 

Disadvantages:  

• Heat produced by the arc may affect the associated switches. 
• They must be replaced after each operation. 

Main circuit breaker: 

MCB acts as a switch and a safety device that can cut off all power supplies entering a house.  

Tripping: If the current exceeds a safe level, a bimetallic strip in the breaker heats up, bends, and opens the circuit. This is sometimes called “tripping” the breaker. Current stops flowing until the breaker cools, and you reset it. 

Advantages: 

• It works quickly on overloading and under voltage. 
• It is reusable hence less maintenance cost and less replacement cost. 

• It is very simple to resume the supply. 
• It can be easily used as a circuit control switch when needed. 
• The performance of MCB is good in case of earth leakage. 

Disadvantages 

• The cost of the MCB is greater than the fuse. 

• The cost of the MCB distribution board is greater than the rewireable fuse board. 

Household wiring: 

Wires from the meter are connected in series to the MCB.  The connection in the service panel is all parallel connection. As the total resistance decreases, current in the circuit increases, thus making the safety devices to be of optimum use.  

All the household circuits are in parallel, so even if one trips, the other will continue to work. 

The wires coming into a house include black, red, and white-colored wires. The black and the red wires are “hot” and are known as live wires. The white wire is neutral – leading to ground.  

1. The black is rated as being 120 V from the neutral  

2. The red is also rated as being 120 V from the neutral such that net potential difference is 240 V.  

3. Neutral wire is the ground. It protects us from electrocution. Service panel has a ground wire. 3 prong plugs – the circular, bottom hole leads to the ground buried outside. 

Grounding the circuit: 

The service panel is connected to a long metal stake that is buried outside the house. If a person is electrocuted most of the current will go to the ground. In older houses the wiring is grounded on copper water pipes. 

Questions and answers 

Question 1: What will happen when outlets in bathrooms are installed near the water sources? 

Answer: A person will get an electric shock, and it is very harmful for their life. 

Question 2: Complete the sentence: 

One should connect less number of appliances to a single plug because——— 

Answer: If too many devices are plugged into one single circuit, then due to the current, the wires get heated to a very high temperature, which may lead to fire. 

Question 3: Which of the wire (live/neutral) will electrocute the user if touched with naked hands? 

Answer: If user touches live wire with naked hands, they will be electricity

Summary

• Series and parallel connections are at home.

• A wire comprises of red wire, black wire and a neutral wire

• A few of the safety equipments used at home are

1. MCB
2. Fuse

• An electrical safety equipment breaks the circuit when excess current flows through it.

• In a 3-prong plug – the circular, bottom hole leads to the ground buried outside.