Electrical Safety Devices (Fuse)

Electrical Safety Devices (Fuse)

by Sanjay Srivastava

​Kendriya Vidyalaya Air Force Station Rajokri, New Delhi

​Electrical Safety Device (Fuse)

In present days, ​the electricity is playing very important and integral part of our life. To use electricity in most useful, effective and friendly way.

​

We must learn about safety issues related to electricity.

​Electrical Safety Device (Fuse)

​ In this unit we will try to learn and understand different issues related to

​

1. Electrical safety and

2. Fuse as safety device

​

​

​ lets go

What is electricity?​

before we start moving forward, lets check or visit our learned areas related to electricity​

​

​

​So, What is electricity?

What is electricity?​

Electricity: -

​Usually the electricity defined as

​

​- a form of energy

​

​or

​

​- as flow of electrical charges.

What is electricity?​

In general sense both statements are accepted for explanation of electricity.

​but its better to say

​

​"The electricity is a form of energy which develops due to the flow of charges."

​In this statement, there are two important terms, we need to understand for better conceptual learning

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​1- Energy (What is energy?) and

​

​

​

​2- Charge (What is charge?)

​

​Energy

​In simple words "energy" can be defined as

​" ability to do the work".

​Charge

​In simple words the charge can be defined as " a property of matter" (property just like mass, volume etc...)

​

​

​ To understand charges much better; we have to recall the basic building particles of a substance.

​

​So; what is basic building block of a substance or element?

​Basic Building Block of Substance

​All the substances are made of small particles, these smallest particles are known as the building blocks of substance.

​

In an element "Atom" is the basic building.

​Structure of atom

An atom is a particle of matter that uniquely defines a chemical element. ​

​Structure of atom

An atom consists of a central nucleus that is usually surrounded by one or more electrons. ​

​Structure of atom

Each electron is negatively charged.

​

The nucleus is positively charged, and contains one or more relatively heavy particles known as protons and neutrons.​

​Structure of atom

These charged particles which posses specific kind of electrical phenomenon are known as charge.

​

​So,

Charges are particles which holds some electrical potential on them; at atomic level electrons and protons are known as " Charge"

​Quiz Time:-

​Answer the following questions:

Multiple Choice

What is electricity?

• Flow of charges

• Form of energy

• Form of energy develops due to the flow of charges

• Invisible form of energy

Multiple Choice

What is energy?

• Ability to do the work.

• Power

• Force

• Capacity to do anything

Fill in the Blanks

Atom is basic

block of a substance.

Multiple Choice

Electrons can also be termed as

• Positive charge

• Neutral charge particles

• Potential charge particles

• Negative charge particles

Multiple Choice

Electron and Proton are two important sub-atomic particles of an atom. They possess some electrical charge on them. Which statement is true for electron and proton?

• Both have equal and similar kind of electrical charges.

• Both have equal but opposite kind of electrical charges.

• Proton has larger electrical charge than electron.

• As electrons keep rotating in the orbit they can gain or lose any kind of charge.

Electrical Safety Device​

That's great, now we can move forward to ..........​

​Safety

​Safety is an important issue in every arena of our life. We had already learned number of safety measures such as

​

• Road Safety

• ​

• Fire Safety etc.

• ​

​we learned that safety is state of being safe or protected from any accident or loss

​Electrical Safety

​The electrical safety refers to the state of being safe or remain protected from any kind of electrical accident or loss.

​Fuse

​When we talk about the electrical safety; then it's equally important to learn about electrical safety devices.

​

​Fuse is one of the most common safety device almost used by all electrical and electronic appliances for enhancing the level of protection.

​What is a fuse?

​Basically Fuse is a special kind of wire. The important specification of wire is

​

• The fuse wire is made of an alloy.

• ​

• ​Fuse wire has good conductivity and allows the current to flow through it.

• ​

• ​Whenever the quantity of flowing current crosses the specified limit; it melts down

Materials used to prepare fuse wire​

​The fuse wire prepared by using number of metals. Such as

• ​Zinc

• ​Copper

• ​Silver

• ​Aluminium

• ​Tin

• ​Lead etc.

Materials used to prepare fuse wire​

For small currents up to 10 A, tin or an alloy of lead and tin (lead 37%, tin 63%) is used for making the fuse element.

Materials used to prepare fuse wire​

For larger currents, copper or silver is employed. 

​

It is a usual practice to tin the copper to protect it from oxidation. 

Materials used to prepare fuse wire​

Zinc (in strip form only) is good if a fuse with considerable time-lag is required i.e., one which does not melt very quickly with a small overload. ​

​Working of fuse.

​The basic working principle of fuse lies on "heating effect of electric current".

​

​(Heating effect of electric Current - whenever electric current flow through any substance, the temperature of substance.)

Working of fuse​

​When we connect the fuse in any electrical circuit, the current flows through the fuse wire.

​

​

​Normal working condition:-

​​During normal working current level the current keeps flowing in the circuit.

Working of fuse​

Over current ​condition: -

Whenever current increases more than specified limit the temperature of fuse wire also increases and finally the fuse wire melt down and breaks the circuit to protect the connected appliance.

​

​

​Connecting Fuse in an electrical circuit

​The Fuse, as a safety/protective device gets connected in the electrical circuit in "Series Connection".

​

In series connection whole current of electrical circuit flows through the connected fuse wire.

​

Fuse wire never gets connected in parallel connection.

​Connecting Fuse in an electrical circuit

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Fuse wire never gets connected in parallel connection.

​Why not connecting Fuse in parallel connection

​As fuse wire is good conductor of electricity, a short circuit condition will develop, if we connect the fuse in parallel.

​

Fuse will blowup immediately.

​Symbolic Representation of fuse

​We had read that most of the electrical and electronic components/ devices are represented by a simple picture.

​

​These pictorial representation are known as Symbol.

​Symbolic Representation of fuse

​Fuse is also represented by unique pictorial representation.

​

​The three accepted standard symbols are shown in diagram.

​

​We are commonly using the curved / waved line picture to represent Fuse.

​​Simple Circuit diagram with fuse

​With Direct Current supply source, the fuse is connected with "Positive Terminal" of circuit.

​Simple Circuit diagram with fuse

​In alternating current supply source; the fuse is connected with phase/ live wire of supply source.

​Types of Fuse

There are different types of fuse. We will discuss some of common types of fuse.

​Rewireable Fuse

​This is very common type of fuse, usually fixed with house wiring.

​

This fuse is also known as Kit-Kat Fuse.

​

​This fuse has two parts - one is fixed and another is removable part.

​Rewireable Fuse

​Fixed Part gets connected with the Phase wire of supply.

​

​

Removable Part's terminal gets connected together through fuse wire.

​Rewireable Fuse

​In kit-kat fuse the blown fuse wire replaced with fresh length of fuse wire.

​

​After connecting fuse wire the removable part get placed within the groves of fixed part.

​

​Now your circuit is ready to work.

​Cartridge Fuse

​The cartridge fuse are also known as sealed or enclosed fuse.

​

​These types of fuse remain packed in glass or casing to protect the electrical and electronic components from spark.

​Cartridge Fuse

​As the Cartridge fuse remains packed in an enclosure.

​

​Can not be rewired.

​

​We use new same size and current rating fuse to replace the blown fuse.

Now it's quiz time​

lets start​

Multiple Choice

What property of fuse wire enables it to act as a safety feature?

• it's Boiling point

• it's strength

• it's Melting point

• it's Texture

• it's flexibility

Multiple Choice

This is the symbol for a...

• Light Emitting Diode

• Fuse

• Fixed Resistor

• Variable Resistor

Multiple Choice

What causes a fuse to blow?

• High Voltage

• High Resistance

• High Current

• High Power

Multiple Choice

what happens to a 3A fuse when the current reaches 3 amperes?

• it sets alight

• it melts

• it explodes

• it cracks

• nothing happens

Multiple Choice

Which label points to the Fuse on the diagram?

• C

• D

• E

• F

Multiple Choice

The purpose of a fuse is to...?

• To break when there is too little current.

• Keep the circuit intact even if there is a problem with the electrical equipment.

• Protect the wiring and equipment from overloading & potentially catching fire.

Multiple Choice

The thicker the wire in a fuse...?

• The more current needed to melt it and break the circuit.

• The less current needed to melt it and break the circuit.

• The longer it will last.

Multiple Choice

A safety device that breaks the circuit when is overloaded by melting a fusible link is called a ____________.

• Circuit Breaker

• Fuse

• GFCI

Multiple Choice

This rewireable fuse is also known as

• Cartridge Fuse

• HRC Fuse

• Semiconductor Fuse

• Kit-kat Fuse

Multiple Choice

The fuse is an alloy, Which combination of metals is appropriate

• Sodium and Lead

• Lead and Oxygen

• Copper and PVC

• Lead and Tin

Multiple Choice

What is fuse?

• Safety Device

• Circuit breaking device

• Conductor jointer

• Thermal Controller

Multiple Choice

Fuse works on principle of ________.

• Chemical Effect of electric current

• Heating effect of electric current

• Magnetic effect of electric current

• Electric field

Multiple Choice

The electrical fuse should be connected in ______ connection only.

• Series

• Parallel

• Either Series or parallel as requirement

• Neither in Series nor in parallel.