What is an Electric circuit?
An electric circuit is an inter connection of electrical elements.
What do you mean by independent and dependent sources?
An ideal independent source is an active element that provides a
specified voltage or current that is completely independent of other
circuit variables where as an ideal dependent source is an active
element in which the source quantity is controlled by another voltage
What are the types of dependent sources?
controlled voltage source
Current controlled voltage source
Voltage controlled current source
Current controlled current source
Explain ohm’s law?
At constant temperature, current flowing through an element is
directly proportional to the potential difference across it.
What is open circuit and short circuit?
An open circuit is a circuit element approaching infinite resistance
and short circuit is a circuit element with resistance approaching
Define a branch, node, loop and mesh?
It represents a single element such as voltage source or resistor.
A node is the point of connection between two or more branches
A loop is any closed path in a circuit
A mesh is a loop which does not contain any other loops in it.
State kirchhoff’s laws?
It states that algebraic sum of currents entering a node is zero.
Sum of currents entering a node=sum of currents leaving it.
It states that algebraic sum of voltages around a closed path or loop
sum of voltage drops=sum of voltage rises.
What is super node and super mesh?
A super node is formed by enclosing a voltage source between two
non-reference nodes and any elements connected parallel with it. A
super mesh results when two meshes have a current source in common
Mesh analysis vs Nodal analysis?
Mesh analysis is more useful when there are many series elements,
voltage sources and we have to find out branch or mesh currents.
analysis is better if there are many parallel connected elements,
current sources and we have to find node voltages.
Explain superposition principle?
The superposition principle states that the voltage across (or
current through) an element in a linear circuit is the algebraic sum
of voltages across (or currents through) that element due to
independent sources acting alone.
What is meant by source transformation?
A source transformation is the process of replacing a voltage source
in series with a resistor R by a current source is
in parallel with a resistor R, or vice versa.
State thevenin’s theorem?
Thevenin’s theorem states that a linear two terminal circuit can be
replaced by an equivalent circuit consisting of a voltage source VTH
series with a resistor RTH
is open circuit voltage at the terminals and RTH
the input or equivalent resistance at the terminals when the
independent sources are turned off.
State Norton’s theorem?
Norton’s theorem states that a linear two terminal circuit can be
replaced by an equivalent circuit consisting of a current source IN
parallel with a resistor RN
is short circuit current through the terminals and RN
the input or equivalent resistance at the terminals when the
independent sources are turned off.
State maximum power transfer theorem?
Maximum power is transferred to the load when load resistance equals
thevenin resistance as seen from the load.
Explain the behavior of capacitor and inductor to D.C?
A capacitor acts as an open circuit to D.C
know that Q=CV
is zero in case of D.C supply. So current is zero which implies it
acts as an open circuit.
inductor acts as a short circuit to D.C
know that V=Ldi/dt
in case of D.C supply. So, voltage across inductor is zero which
implies it acts as a short circuit.
What are different parameters used to represent two port networks?
two port network can be modeled using six parameters
(Z),Admittance (Y),Hybrid (h),Inverse hybrid (g),Transmission (T) and
Inverse transmission (t) parameters.
Q:How tube light circuit is connected and how it works?
A:A choke is connected in one end of the tube light and a starter is in series with the circuit. When supply is provided ,the starter will interrupt the supply cycle of AC. Due to the sudden change of supply the chock will generate around 1000volts . This volt will capable of to break the electrons inside the tube to make electron flow. once the current passes through the tube the starter circuit will be out of part. now there is no change of supply causes choke voltage normalized and act as minimize the current.
Q:whats is MARX CIRCUIT?
A:It is used with generators for charging a number of capacitor in parallel and discharging them in series.It is used when voltage required for testing is higher than the available.
Q:What is encoder, how it function?
A:An encoder is a device used to change a signal (such as a bitstream) or data into a code. The code may serve any of a number of purposes such as compressing information for transmission or storage, encrypting or adding redundancies to the input code, or translating from one code to another. This is usually done by means of a programmed algorithm,especially if any part is digital, while most analog encoding is done with analog circuitry.
Q:What are the advantages of speed control using thyristor?
1. Fast Switching Characterstics than Mosfet, BJT, IGBT 2. Low cost 3. Higher Accurate.
Q:Why Human body feel Electric shock ?? n in an Electric train during running , We did nt feel any Shock ? why?
A:Unfortunately our body is a pretty good conductor of electricity, The golden rule is Current takes the lowest resistant path if you have insulation to our feet as the circuit is not complete (wearing rubber footwear which doing some repairs is advisable as our footwear is a high resistance path not much current flows through our body).The electric train is well insulated from its electrical system.
Q:what is the principle of motor?
A:Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movemnt is called as torque.It is based on farady’s laws of electromagnet induction.
Q:What is electric traction?
A:Electric traction means using the electric power for traction system (i.e. for railways,trams, trolleys etc). Electric traction means use of the electricity for all the above machines. Now a days, magnetic traction is also used for bullet trains.and basically dc motors are used for electric traction systems.
Q:How can you start-up the 40w tube lite with 230v AC/DC without using any choke/Coil?
A:It’s possible by means of Electronic chokes,otherwise it’s not possible to ionize the particles in tube light with normal voltage.
Q:What is “pu” in electrical engineering?
A:Pu stands for per unit and this will be used in single line diagram of power distribution and it is like a huge electrical circuit with no of components (generators, transformers, loads) with different ratings (in MVA and KV). To bring all the ratings into common platform we use pu concept in which, in general largest MVA and KV ratings of the component is considered as base values, then all other component ratings will get back into this basis.Those values are called as pu values. (p.u=actual value/base value).
Q:Operation carried out in Thermal power stations?
A:The water is obtained in the boiler and the coal is burnt so that steam is obtained this steam is allowed to hit the turbine , the turbine which is coupled with the generator generates the electricity.
Q:Why link is provided in neutral of an ac circuit and fuse in phase of ac circuit?
A:Link is provided at a Neutral common point in the circuit from which various connection are taken for the individual control circuit and so it is given in a link form to withstand high Amps. But in the case of Fuse in the Phase of AC circuit it is designed such that the fuse rating is calculated for the particular circuit (i.e load) only.So if any malfunction happen the fuse connected in the particular control circuit alone will blow off.
Q: What is the difference between electronic regulator and ordinary electrical rheostat regulator for fans?
A:The difference between the electronic and ordinary electrical regulator is that in electronic regulator power losses are less because as we decrease the speed the electronic regulator gives the power needed for that particular speed but in case of ordinary rheostat type regulator, the power wastage is same for every speed and no power is saved.In electronic regulator, triac is employed for speed control by varying the firing angle speed and it is controlled but in rheostatic ,control resistance is decreased by steps to achieve speed control.
Q:Why, when birds sit on transmission lines or current wires doesn’t get shock?
A:Its true that if birds touch the single one line (phase or neutral) they don’t get electrical shock… if birds touch 2 lines than the circuit is closed and they get electrical shock.. so if a human touch single one line(phase) then he doesn’t get shock if he is in the air (not touching – standing on the ground if he is standing on the ground then touching the line (phase) he will get a shock because the ground on what we standing is like line (ground bed – like neutral)? and in the most of electric lines the neutral is grounded..so that means that human who touch the line closes the circuit between phase and neutral.
Q:what is meant by armature reaction?
A:The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.
Q:what happen if we give 220 volts dc supply to d bulb r tube light?
A:Bulbs [devices] for AC are designed to operate such that it offers high impedance to AC supply. Normally they have low resistance. When DC supply is applied, due to low resistance, the current through lamp would be so high that it may damage the bulb element.
Q:Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?
A:DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.
Q:what is ACSR cable and where we use it?
A:ACSR means Aluminium conductor steel reinforced, this conductor is used in transmission & distribution.
Q:What is vaccum currcuit breaker.define with cause and where be use it Device?
A:A breaker is normally used to break a ciruit. while breaking the circuit, the contact terminals will be separated. At the time of seperation an air gap is formed in between the terminals. Due to existing current flow the air in the gap is ionised and results in the arc. various mediums are used to quench this arc in respective CB’s. but in VCB the medium is vaccum gas. since the air in the CB is having vaccum pressure the arc formation is interrupted. VCB’s can be used upto 11kv.