## Saturday, 24 September 2011

### Basic Electrical Engineering Interview Questions 1

What is Current?
Current can be deﬁned as the motion of charge through a conducting material. The unit of current is Ampere whilst charge is measured in Coulombs.
The quantity of total charge that passes through an arbitrary cross section of a conduct-ing material per unit second is deﬁned as an Ampere.”
Mathematically,
I =Q/t
or Q = It
where Q is the symbol of charge measured in Coulombs (C), I is the current in amperes (A) and t is the time in seconds (s).
Could you measure current in parallel?
No,Current is always measured through(in series with) a circuit element.
What Is the difference between Voltage or Potential Difference? And What are they?
Voltage or potential difference between two points in an electric circuit is1V if 1J (Joule) of energy is expended in transferring 1 C of charge between those points.
It is generally represented by the symbol V and measured in volts (V). Note that the symbol and the unit of voltage are both denoted by the same letter, however, it rarely causes any confusion.
The symbol V also signiﬁes a constant voltage (DC) whereas a time-varying (AC) voltage is represented by the symbol v or v(t)
Could you measure Voltage in series?
No, Voltage is always measured across(in parallel with) a circuit element
How many Types of Circuit Loads are there in a Common Electrical Circuit?
A load generally refers to a component or a piece of equipment connected to the output of an electric circuit. In its fundamental form, the load is represented by any one or a combination of the following:
1. Resistor (R)
2. Inductor (L)
3. Capacitor (C)
A load can either be of resistive, inductive or capacitive nature or a blend of them. For example, a
light bulb is a purely resistive load where as a transformer is both inductive and resistive. A circuit
load can also be referred to as a sink since it dissipates energy whereas the voltage or current supply can be termed as a source.
What are the different Sign Conventions used in electric circuits?
It is common to think of current as the ﬂow of electrons. However, the standard convention is to take the ﬂow of protons to determine the direction of the current.
In a given circuit, the current direction depends on the polarity of the source voltage. Current always ﬂow from positive (high potential) side to the negative (low potential) side of the source as shown in the schematic diagram of Figure 2.4(a) where Vs is the source voltage, VL is the voltage across the load and I is the loop current ﬂowing in the clockwise direction.
In Source current leaves from the positive terminal
In Load (Sink) current enters from the positive terminal
What do you mean by Passive Circuit Elements and why these are called Passive?
Passive Circuit Elements:
Resistor, Capacitor, Inductor
State and define Ohm’s Law?
It is the most fundamental law used in circuit analysis. It provides a simple formula describing the
voltage-current relationship in a conducting material.
Statement:
The current through a conducting material is directly proportional
to the voltage or potential difference across the material.
I ∝ V
V = RI or I =V/R
or R =V/I
where the constant of proportionality R is called the resistance or electrical resistance, measured in ohms (Ω).
Please Define Ohm’s Law for A.C(Alternating Current)?
Everything else would remain same only the resistance will be replaced with Impedance, which is defined as the opposition to the flow of A.C.
What is the function of Capacitor in Electrical Circuits?
A capacitor is a passive circuit element that has the capacity to store charge in an electric ﬁeld. It is widely used in electric circuits in the form of a ﬁlter.
Why Inductors are installed in electrical Circuits?
An inductor is a piece of conducting wire generally wrapped around a core of a ferromagnetic material. Like capacitors, they are employed as ﬁlters as well but the most well known application is their use in AC transformers or power supplies that converts AC voltage levels.