January 2011|Online electrical engineering & Electrical Interview Questions

Saturday, January 29, 2011


Here is the next question about the Fan Speed Regulator.
Will the power consumption  be same for normal regulator and electronic regulator at same speed ?
The answer to this would be no.The reason behind this is normal regulator uses resistances for the speed control of the fan.So the resistances will act as a potential divider,and the applied voltage to the fan changes the based on the resistance position.

At maximum speed the full voltage is applied.When the regulator position is decreased,resistance would be introduced and the voltage applied to the fan decreases which in turn reduces the speed of the fan.When the regulator position is kept at low speed, the power wastage across the resistance will be more.
Therefore the overall efficiency of the normal speed regulator is poor.

The electronic speed regulator uses the semi conductor devices.The voltage regulator is used to change the applied voltage to the fan.So the power loss is negligible in the electronic fan speed regulator.Therefore overall efficiency of the electronic regulator is high.


Hi guys...I am answering to one of the doubts posted in the comments section.This electrical question is regarding the Fan Speed Regulators.

1.What is the difference between electronic regulator and normal regulator in fan?
i) You would have noticed the old normal regulators in some old bungalows and some government buildings.Normal fan regulator is huge in size whereas electronic regulator is small in size with just a knob to control the speed.
ii) Speed variation is in steps in the normal regulators whereas in electronic speed regulators we can obtain smooth speed control.
iii) Normal fan speed regulators use resistances(works as potential divider network) for controlling the speed whereas the electronic speed regulator uses the voltage regulator which changes the input voltage to the fan thereby changing the speed of the fan.
iv) Heat dissipation is more in the normal fan speed regulators whereas in electronic regulators there is negligible heat dissipation.
v) Since the heat dissipation is more in the normal regulators, it will be provided with some holes at the sides for ventilation and are mounted outside the switch board.
vi) The electronic regulator will be mounted inside the switch board(the device) and only the control knob will be outside the switch board.

Monday, January 24, 2011


These are the most frequently asked Electrical Interview Questions from Transmission & Distribution.
During my interview, i said my area of interest is Transmission & Distribution.Then i was bombarded with the following questions.

Why do we go for higher voltage transmission lines?
There are many advantages in transmitting the power at high voltages.Because for the same power,the copper loss(I^2R loss) will be less for higher voltages,since power= V*I.There for current value decreases thereby decreasing the power loss.

Why do we prefer overhead transmission line over under ground transmission line?
  • The cost of the conductors used in over head lines in much lesser when compared to the under ground lines.
  • The under ground lines need perfect insulation so it is provided with extra insulation which increases the cost.
  • It is very difficult to identify and repair the faulty part in the under ground transmission lines.
  • Skin effect and Proximity effect are more in under ground lines than the Over head transmission lines.

Thursday, January 20, 2011


Hey friends..Let me share the Electrical Interview questions which i faced during my interviews.If you are attending interview for any software companies,the questions would be on basics of Electrical Engineering.

What is the difference between motor and generator ?
       Motor is an electrical device which converts electrical energy into mechanical energy where as Generator is an electrical device which converts mechanical energy to electrical energy.

What are the types of Motor and Generator?
        Basically both motors and generators are classified as DC and AC. 
Further DC motor is classified as DC Series motor,DC Shunt motor,DC Compound motor.
AC motor is classified as 1 phase motor and 3 phase motor and Synchronous motor.
There are special machines such as Brushless DC motor,Universal motor,Stepper Motor,Hysteresis motor.

DC generator as classified as separately exicited DC generator,DC Series generator,DC shunt generator,DC compound generator.AC generators are called as alternators.Alternators are single phase and three phase alternators.There is also Synchronous generator.

Thursday, January 6, 2011


In almost every electrical interview this question is asked "What is Current?".

Current is nothing but the movement of electric charge that occurs in a closed circuit.Flow of electrons is from negative terminal to positive terminal.The conventional current direction is opposite to the direction of electron flow.

In analogy terms,current is equivalent to water flow in a pipe.When pipe is closed there is no water flow and when it is opened there is a flow of water.Similarly when insulators are used in a circuit,it opposes current flow by arresting the movement of electrons and when a conductor is used in a circuit,it allows the current to flow through.