Trees are the primary cause to interruptions in distribution lines.  Branches of trees may reach out for the lines causing earth faults.  A branch which breaks during a storm and falls on a line can cause short-circuits or cause the conductor to break and fall resulting in death to people below.
Hence, it is necessary that every distribution system has a comprehensive tree management program,  Trees along a distribution line should be periodically inspected and periodically pruned to prevent any contact with the lines.    

In forested areas, trees below transmission lines can be cut and replaced with vegetation which does not grow too high.  This Tree clearing can be done once every 6 to 12 years.  

Weak trees which can fall on the lines shoudld be identified and cut down.  

Tree Maintenance should be done taking the help of a qualified arborist (a person who specialises in trees

Grounding Loops are a phenomenon we come across in signal cables.  The shield of the signal cables is intended to prevent interference from stray magnetic fields.  This shielding needs to be grounded at only one point.  

If the shielding is grounded at two points, there is a possibility that the two earth points may not really be at the same potential.  This can result in the flow of current through the shield.  This current which flows through the shield will create a magnetic field which can interfere with the signal cable.
Ground Loop
Grounding Loops can be prevented by ensuring that the shielding is grounded at only one end.  The other end should be taped and isolated.

An electrolyte is a solution which consists of ions which facilitate conduction.  A solution of sodium chloride in water is an example of an electrolyte.  The sodium  and the hydroxyl ions conduct electricity.  This form of conduction is called ionic conduction which is different from the electronic conduction in metals.   

In Electrical Engineering, Electrolytes are important parts of batteries and in the process such as lectroplating and electro refining. 

Salts when melted can also be called electrolytes.  Sodium Chloride when heated above its melting point conducts electricity in the molten state.  

Electrolytes are classified into strong electrolyte or weak electrolytes depending on the concentration of ions in the solution.  

Pritned Circuit Boards also known as PCBs are integral components of almost all electronic devices such as cellphones, tablets, tv remotes and radios.  A Printed Circuit Board is made of a fibreglass, composite epoxy or a laminate material.  The board contains a number of tracks which are etched on the board.  These tracks are usually made of copper.  They are sometimes coated with nickel or gold to protect against corrosion.  

The board contains holes where components such as transistors, resistors, capacitors can be mounted.  These components are fitted on these holes and then soldered.  The components are connected to each other through the conductive traces.

A PCB contains two sides. The component side and the track side.  The component side contains the various components while the track side contains the tracks.  

Nowadays, there are multi-track PCBs as well which contain many tracks in the form of layers in a single board.  Printed Circuit boards used for graphic adaptors or mother boards can have as many as 12 layers. 


Lithium Ion Batteries find wide application in mobile phones and other electronic devices.  In Lithium ion batteries, Lithium metallic oxide is the anode while carbon is used as the negative electrode.  Lithium ions are transferred between the lithium oxide anode and the carbon electrode during charging and in the opposite direction while discharging.  

The higher power density and the high voltage per cell (3.6 V) ensures that a single battery can be used.   Lithium Battery can hold charge more effectively than other batteries.  A typical lithium battery loses 5% of its energy every month.  

Lithium ion battery packs typically have a small in built electronic control device which continually monitors the temperature, voltage and current.  It shuts down the battery when there is a deviation from established limits.  

Lithium Ion batteries are extremely sensitive to temperature and can degenerate faster.  The Lithium battery should never be completely discharged. If that happens the chip which controls the battery will no longer be powered.  The battery cannot be used again.  

There have been rare cases when lithium ion batteries catch fire.  This is mostly due to defects in the manufacturing process.  

Hopkinson's Law describes the relationship between the reluctance of a magnetic circuit, the magnetomotive force and the magnetic flux.  It is similar to Ohm's Law

Ohm's Law defines the relationship between voltage, current and resistance

It is described as

Voltage = Current x Resistance

Similarly, Hopkinson's Law can be written as

Magnetomotive Force =  Flux x Reluctance

Hopkinson's Law is also known as Rowland's Law

Inductance is the property of an electric circuit to resist the change in current.  A current flowing through a wire has a magnetic field around.  The magnetic flux depends on the current and when the current varies, the magnetic flux varies with it too.  When the magnetic flux varies, an emf is developed across the conductor in accordance with Faraday's law.  

This emf is in the direction opposite to the direction of the current as postulated by Lenz' Law.  The emf induced can be described by the equation below
Inductance Equation

Where V is the voltage, L is the inductance in henry and I is the current.  

The unit of inductance is Henry, named in honour of Joseph Henry who first discovered self-inductance.  The symbol of inductance is L, in honour of Heinrich Lenz who postulated Lenz' Law which describes the direction of the emf induced.




Arc Welding is one of the many ways of welding two metals.  During welding, two metals melt and intermix.  The mixture ensures that the finished weld has the same physical properties as that of the  base metals.  

In arc welding, the high temperature required for the weld is generated by means of an electric arc.  An AC or DC power source has one of its terminals connected to the workpiece.  The other piece is connected to the electrode holder.  

The Arc is created when the electrode is made to touch the workpiece and withdrawn a few millimetres.  The interruption in current, triggers the arc.  

The high temperature of the arc which is around 3500 degrees celsius causes the base metal and the welding electrode to melt.  A pool of metal is created as the electrode is moved across the workpiece.  This pool solidifies and creates a fusion bond.

Arc Welding can be done with both AC and DC supplies.  The choice is made based on the requirement of depth of penetration and deposition rate.

Arc Welding is done by means of a welding Transformer or special welding units.  

The different parts of a dc machine are

1. Yoke

The Yoke provides shape to the dc machine.  It provides mechanical support to the poles.  It also provides a low reluctance path for the magnetic flux.  The Yoke is usually constructed of cast iron or steel.

2. Poles

The Poles produce the magnetic flux from the field current.  The pole consists of windings made of copper which are wound on to a core made of cast iron.  The field winding is connected in series or parallel to the the main winding.

3. The Pole Shoe

The Pole shoe is an extension of the pole.  The pole shoe acts as a "lens" to the magnetic flux and helps spread the flux uniformly over the armature.

4. The armature Core

The armature core is made of Electrical Steel.  It function of the core is to hold the armature windings in slots.  It also serves as a path for the magnetic flux through the machine.  The core is made of laminations to prevent eddies.

5. The Commutator

The commutator helps collect the emf built in the core windings.  The commutator consists of copper segments which are insulated from each other.  Mica is usually used for insulation.  The segments of the commutator are connected to the coils of the armature.

6. Brushes

The Brushes in a dc machine are made of carbon.  Carbon has the property of self-lubrication.  The carbon is usually sintered with copper to provide better conductivity.  The brushes are spring loaded so that they have better contact with the commutator surface.  The brushes serve to collect the emf generated in the machine.  The brushes slide over the commutator such that the current direction is always in the same direction.  Thus a pulsating direct current is obtained from the alternating voltage of the armature core.


7. Windings

The windings carry the current in the dc machine.  The windings are made of copper and are placed in slots in the core.  The windings are wound as a wave winding or a lap winding depending on the current the windings will carry.

Prismatic batteries are batteries which are shaped in a rectangular or a square format.  These batteries are thin and are thus ideal for mobile phones and laptops.  

In prismatic batteries, the anode and the cathode are made in the form of sheets with the separator sheet between them.   Prismatic batteries are being made with higher power ratings aimed at the hybrid vehicle market.  They are, however, less efficient than the cylindrical battery.

Immersion heaters are heaters in which the heating elements come in direct contact with the medium. Immersion heaters are used to heat water and other non-flammable liquids which are held in containers made of stainless steel or glass.  

Since, the heat generated in the elements is directly passed on to the medium, the efficiency of immersion heaters is almost 100%.  Immersion heaters usually come with a thermostat which is usually mounted above the elements in an insulated box.  

Immersion heaters used for heating corrosive media are designed with special corrosion resistant materials. Immersion heaters come in a range of piping options such as welded, flanged and threaded.  

When used with water or any other conductive material, care should be taken to earth the vessel and the heater body as there may be a risk of electric shock in case of current leakage within the elements.  


Arc Welding is one of the many ways of welding two metals.  During welding, two metals melt and intermix.  The mixture ensures that the finished weld has the same physical properties as that of the  base metals.  

In arc welding, the high temperature required for the weld is generated by means of an electric arc.  An AC or DC power source has one of its terminals connected to the workpiece.  The other piece is connected to the electrode holder.  

The Arc is created when the electrode is made to touch the workpiece and withdrawn a few millimetres.  The interruption in current, triggers the arc.  

The high temperature of the arc which is around 3500 degrees celsius causes the base metal and the welding electrode to melt.  A pool of metal is created as the electrode is moved across the workpiece.  This pool solidifies and creates a fusion bond.

Arc Welding can be done with both AC and DC supplies.  The choice is made based on the requirement of depth of penetration and deposition rate.

Arc Welding is done by means of a welding Transformer or special welding units.