HOLDING CURRENT

HOLDING CURRENT
It is the maximum anode current, gate being open, at which SCR is turned off from ON conditions.

When Semi conductor Rectifier is in the conducting state, it cannot be turned OFF even if gate voltage is removed.  The only way to turn off or open the SCR is to reduce the supply voltage to almost zero at which point the internal transistor comes out of saturation and opens the SCR.  The anode current under this condition is very small (few mA) and is called Holding current.  If an SCR has a holding current of 5mA, it means that if anode current is made less than 5mA, then SCR will be turned off.

PEAK REVERSE VOLTAGE

PEAK REVERSE VOLTAGE
It is the maximum reverse voltage (cathode positive w.r.t anode) that can be applied to an SCR without conducting in the reverse direction.

Peak reverse voltage(PRV) is an important consideration while connecting an SCR in an a.c circuit. During the negative half of a.c supply, reverse voltage is applied across SCR.  If PRV is exceeded, there may be avalanche breakdown and the SCR will be damaged if the external circuit does not limit the current.  

BREAKOVER VOLTAGE

BREAKOVER VOLTAGE
It is the minimum forward voltage, gate being open, at which  Semi Conductor Rectiver(SCR) starts conducting heavily i.e turned on

if the breakover voltage of an SCR is 220V, it means that it can block a forward voltage as long as the supply voltage is less than 220V.  If the supply voltage is more than this value, the SCR will be turned on.  In practice SCR is operated with supply voltage less than breakover voltage and it is then turned on by means of a small voltage applied to the gate.

SILICON CONTROLLED RECTIFIER (SCR)

SILICON CONTROLLED RECTIFIER (SCR)
is a semiconductor device that acts as a true electronic switch.  It can change alternating current into direct current and at the same time can control the amount of power fed to the load.  SCR combines the features of a rectifier and a transistor.

MERITS AND DEMERITS OF MULTIMETER

Multimeter is widely used for manufacturing and servicing of electrnoics equipment.  It has its own merits and demerits.

Merits:
It has a single meter which performs several measuring functions
it can make measurements with reasonable accuracy

Demerits:
It cannot make precise and accurate measurements due to the loading effect
Technical skill is required to handle it.

WHAT IS MULTIMETER SENSITIVITY

The resistance offered per volt of full scale deflection by the multimeter is known as multimeter sensitivity. it indicates the internal resistance of the multimeter.  If the sensitivity of a multimeter is high, it means that it has high internal resistance. when such a meter is connected in the circuit to read voltage, it will draw a very small current.  if the sensitivity is low, it would cause serious error in voltage measurement.

WHAT IS MULTIMETER

Multimeter is an electronic instrument used for measuring resistances, current and voltages. it can be used for measuring D.C aswell as A.C voltages and currents.

WHAT ARE THE APPLICATIONS OF MULTIMETER

A multimeter is used for
1)checking the circuit continuity.
2)measuring d.c. voltages across various resistors in electronic circuits.
3)measuring d.c current flowing through the cathode, plate, screen and other vacuum tube circuits
4)measuring a.c. voltages across power supply transformers
5)ascertaining whether or not open or short circuit exists in the circuit.

APPLICATIONS OF VTVM

A VTVM is used for 
1) D.C Voltage measurements:
A VTVM can accurately measure the D.C voltages in an electronic circuits.  

2)D.C Current Measurements:
VTVM does not incorporate a current scale, however current values can be found indirectly.

3)A.C voltage Measurements:
For measuring A.C voltage, a rectifier is used in conjunction with a VTVM.

4)Resistance measurements:
VTVM has ability to measure resistance upto 100 M ohms

VACUUM TUBE VOLTMETER (VTVM)

VTVM is extensively used for measuring both A.C and D.C voltages.  The Vacuum tube voltmeter has high internal resistance (>10 M ohms) and draws extremely small current. The loading effect is very small. A VTVM measures the exact voltage even across a high resistance.  A vacuum tube voltmeter consists of voltmeter and electron tubes.

WHAT IS DIAC

A Diac is a two terminal, three layer bidirectional device which can be switched from its OFF state to ON state for either polarity of applied voltage.  The diac can be constructed in either npn or pnp form.

MERITS AND DEMERITS OF VTVM (VACUUM TUBE VOLTMETER)

A VTVM is an extremely important electronic equipment and is widely used for making different measurements in electronic circuits.

Merits:
* A VTVM draws extremely small current from the measuring circuit.  therefore it gives accurate readings.

* VTVM uses triodes, the voltage to be measured is amplified.  This permits the use of less sensitive meter.

*There is little effect of temperature variations

*It has wide frequency response

Demerits:
*Accurate readings can be obtained only for sine waves.

*It cannot make current measurements directly.

WHAT IS VAT

VAT is a tax levied and collected on the value added to any goods each time they change hand

WHAT ARE THE FEATURES OF VAT

1) VAT is a tax levied and collected on the value added to any goods each time they change hand
2)The transaction shall a sale
3)Sale shall be made by a registered dealer
4)VAT shall be payable at every point of sale
5)Input tax credit shall be admissible on the input tax paid in respect of previous purchases
6)Output tax shall be collected on every sale
7)VAT is applicable for intrastate trade
8)VAT ensures with uniform rates and procedures. It ensures transparency and reduction in consumer prices.

WHAT IS 80C TAX DEDUCTION

General deduction for investment in PPF, PF, LIC,ULIP, Stamp duty on house, Fixed deposits for 5 years, bonds, Contribution to statutory PF or Recognised PF, For LIC policy must be in self or spouse's or any child's name.  Premium paid towards LIC policy not exceeding 20% of the total sum assured.  Repayment of housing loan principal towards self occupied residential property. Payment of tuition fees towards any two children of the assesses.

WHAT IS TAX DEDUCTION AT SOURCE

TDS means Tax Deduction at Source
In simple terms, TDS is the tax getting deducted from the person receiving the amount (Employee/Deductee) by the person paying such amount (Employer/Deductor) 

Empoyee's income Tax is deducted at source means his tax on income is deducted by the employer (who is paying salary), employer pays the same to the income tax department.

WHAT IS CIN

Challan Identificaiton Number, is stamped on the acknowledgement receipt to uniquely identify the tax payment.  CIN has to be quoted in the return of income as a proof of payment.

WHAT IS CHALLAN IDENTIFICATION NUMBER

Challan Identificaiton Number, is stamped on the acknowledgement receipt to uniquely identify the tax payment.  CIN has to be quoted in the return of income as a proof of payment.

PROCEDURE FOR PAYMENT OF DIRECT TAXES AT BANKS

If you are paying taxes in cash at any designated bank branch or by cheque at the bank branch where you have a bank account, the bank will accept your cash/ cheque and will immediately stamp the counterfoil of the challan with a rubber stamp containing the CIN.  If however, you are paying taxes by cheque/draft at a bank branch other than where you have a bank account, the collecting bank branch will accept your cheque/draft and issue you a paper token in acknowledgement.  When you present this token after encashment of the cheque, the bank will hand over the acknowledgement counterfoil duly stamped with the CIN.

WHAT IS PAN

PAN means Permanent Account Number, is a ten digit alphanumeric number issued by the income tax department.

WHAT IS TAN

TAN Means  Tax Deduction Account Number
TAN is a unique identification number for person deducting the tax. The person who is liable to deduct the tax should obtain a TAN before deducting such Tax.

DIFFERENCE BEETWEEN BUSINESS AND PROFESSION

Business, simply means any trade, commerce,manufacturing activity, or any adventure or concern in the nature of trade, commerce and manufacture.

Profession,  a job requiring some thought, skill and special knowledge like that of  C.A, Lawyer, Engineer, Doctor, Architect etc.,

WHAT ARE CORPORATES

Companies or Branches of companies registered under companies Act 1956.

WHO IS DEDUCTOR

Deductor is a person/company who is liable to deduct the Tax at source, from the payment being made to the party, Deductor is also termed as Employer.

WHAT IS TDS

TDS means Tax Deduction at Source
In simple terms, TDS is the tax getting deducted from the person receiving the amount (Employee/Deductee) by the person paying such amount (Employer/Deductor) 

Empoyee's income Tax is deducted at source means his tax on income is deducted by the employer (who is paying salary), employer pays the same to the income tax department.

WHAT ARE LOCAL TAXES

TAXES LEVIED BY MUNICIPAL/ LOCAL TAXES

Property/Building tax levied by local bodies.
Agriculture income tax levied by State governments on income from plantations.

WHAT ARE INDIRECT TAXES

Excise Duty, Customs Duty, Service Tax, Securities Transaction Tax

WHAT ARE DIRECT TAXES

Tax on Corporate income, Capital gains tax, income tax, Tax incentives.

ON WHICH ITEMS OR MATERIAL STATE GOVERNMENT COLLECT TAX

State Government levies taxes on Value Added Tax (VAT), stamp duty, State Excise, land revenue and tax on professions

ON WHICH ITEMS OR MATERIAL CENTRAL GOVERNMENT COLLECT TAX

Central Government levies taxes on income ( except income on agricultural income, which state government can levy), custom duties, central excise and service tax.

WHAT IS CATHODE RAY OSCILLOSCOPE

CATHODE RAY OSCILLOSCOPE:
Cathode ray Oscilloscope is an electronic device which is capable of giving a visual indication of a signal wave form. It is widely used for troubleshooting radio and television receivers.

WHAT IS CATHODE RAY TUBE

CATHODE RAY TUBE:
Cathode Ray Tube is the heart of the oscilloscope.  It is a vacuum tube of special geometrical shape and converts an electrical signal into visual one.  A cathode ray tube makes available plenty of electrons.  These electrons are accelerated to high velocity and are brought to focus on a fluorescent screen.  The electron beam produces a spot of light wherever it strikes.

WHAT IS MICRO ELECTRONICS

MICRO ELECTRIONICS:
Micro Electronics is the branch of electronics engineering which deals with micro circuits.  A micro circuit is simply a miniature assembly of electronic components. e.g Integrated circuit.

WHAT IS AN INTEGRATED CIRCUIT

INTEGRATED CIRCUIT:
An Integrated Circuit is one in which circuit components such as transistors, diodes, resistors, capacitors etc. are automatically part of a small semiconductor chip.

An integrated circuit consists of a number of circuit components ( e.g transistors, diodes, resistors etc) and their inter connections in a single small package to perform a complete electronic function.

WHAT IS MONOLITHIC IC

MONOLITHIC IC:
Monilithic IC is one in which all components and their inter connections are formed on a single thin wafer called substrate.

WHAT ARE HYBRID PARAMETERS

HYBRID PARAMETERS:
Every Linear Circuit having input and output terminals can be analysed by four parameters (one measured in ohm, one in mho and two dimensionless) called hybrid parameters

Hybrid means "mixed".  Since these parameters have mixed dimensions, they are called hybrid parameters.

WHAT IS DIGITAL SIGNAL

Digital Signal:
A Signal (Voltage or Current) that can have only two discrete values is called a digital signal.  A square wave is a digital signal because this signal has only two values. +5V and OV and no other value.

WHAT IS ANALOG SIGNAL

Analog Signal:
A continuously varying signal (Voltage or Current) is called an analog signal.  An alternating voltage varying sinusoidally is an analog signal.

WHAT IS DIGITAL CIRCUIT

Digital Circuit:
An electronic circuit that handles only a digital signal is called a digital circuit.

WHAT ARE LOGIC GATES

LOGIC gates:
A digital circuit with one or more input signals but only one output signal is called a logic gate. Logic gate is a switching circuit.

WHAT ARE THREE BASIC LOGIC GATES

Three Basic Logic Gates:
A Logic gate is a circuit that has one or more input signals but only one output signal.  All logic gates can be analysed by constructing a truth table.  A truth table lists all input possibilities and the corresponding output for each input.

The three basic logic gates that make up all digital circuits are 
1) OR gate  2)  AND gate  3) NOT gate  

WHAT IS OR GATE

OR gate:
OR gate has two or more inputs but only one output. The output y of an OR gate is low when all the inputs are low. The output y of an OR gate is High if any or all the inputs are High.

WHAT IS NOT GATE OR INVERTER

NOT gate:
NOT gate or inverter  has only one input and one output, where the output is opposite of the input. The Not gate is also called "inverter" because it inverts the input.

WHAT IS AND GATE

AND gate:
AND gate is a logic gate that has two or more inputs but only one output.  The output y of AND gate is High when all inputs are high.
The output y of AND gate is low if any or all inputs are low. it is also called "all or nothing gate".  Output will be high when both the inputs are high.

NOT GATE FROM NAND GATE

NOT gate from NAND gate:

When two inputs of NAND gate are joined together so that it has one input, the resulting circuit is NOT gate.

NAND Gate is a Universal Gate

NAND gate is a universal gate because its repeated use can produce other logic gates.

WHAT IS NOR GATE

NOR gate:
It is a combination of OR gate and NOT gate.  Output of OR gate is connected to the input of a NOT gate.

WHAT IS NAND GATE

NAND gate:
It is a combination of AND gate and NOT gate.  Output of AND gate is connected to the input of a NOT gate.

WHAT IS DEMORGAN'S THEOREMS

Demorgan's theorems are used in simplifying expressions which includes a product or sum of variables is inverted

Demorgan's First Theorem:

When the OR sum of two variables is inverted, this is equal to inverting each variable individually and then ANDing these inverted variables.

________          ____   _____

A + B    =     A    .  B

Demorgan's Second Theorem:

When the AND product of two variables is inverted, this is equal to inverting each variable individually  and the ORing them.

______    ___       ___

(A . B ) =   A      +  B

WHAT IS ENCODER AND DECODER

Encoder

The Circuit that converts decimal form to digital (binary) form is called Encoder

Decoder

The circuit that converts digital form to decimal form is called decoder