Workshop

Question 1

What does Kirchhoff’s Current Law (KCL) state?

Answer 1

The algebraic sum of currents entering and leaving a node at any instant of time must be equal to zero.

Question 2

What is the equation representing Kirchhoff’s Current Law?

Answer 2

I = I1 + I2 + I3

Question 3

What does Kirchhoff’s Voltage Law (KVL) state?

Answer 3

In a closed circuit, the algebraic sum of all source voltages must be equal to the algebraic sum of all the voltage drops.

Question 4

What is the equation representing Kirchhoff’s Voltage Law?

Answer 4

V = V1 + V2 + V3

Question 5

What is Thevenin’s Theorem?

Answer 5

A complex, linear bilateral network can be replaced by a simple network containing a Voltage source Vth in series with a resistance Rth.

Question 6

What is the significance of Vth in Thevenin’s Theorem?

Answer 6

Vth is the open circuit voltage between the terminals from where the circuit is being replaced.

Question 7

What does Rth represent in Thevenin’s Theorem?

Answer 7

Rth is the equivalent resistance between the terminals after replacing all sources by their internal resistances.

Question 8

What is the principle of Superposition Theorem?

Answer 8

In any linear bilateral network, the resultant current/voltage in any branch is the algebraic sum of currents/voltages caused by each independent source acting alone.

Question 9

What is true power in an AC circuit?

Answer 9

The power actually consumed in an AC circuit, also known as Real power or Active power.

Question 10

How is Active power calculated?

Answer 10

P = V x I x cos(Ø)

Question 11

What is Reactive power?

Answer 11

Power consumed in inductor and capacitor, calculated as Q = V x I x sin(Ø).

Question 12

What does Apparent power represent?

Answer 12

Apparent power is given by S = VI volt-amperes (VA).

Question 13

What is the formula for Reactive power?

Answer 13

Q = VI sin(Ø) volt-amperes reactive (VAR).

Question 14

What is the definition of a node in electrical circuits?

Answer 14

A point in a circuit where two or more circuit elements are connected.

Question 15

What is the difference between Electric network and Electric circuit?

Answer 15

An electric network is a combination of various components, while an electric circuit is a closed path through which current flows.

Question 16

Fill in the blank: The algebraic sum of current meeting at a node is ______.

Answer 16

zero

Question 17

True or False: KVL can be verified by measuring voltages across resistors in a closed loop.

Answer 17

True

Question 18

What equipment is used to measure power in a single-phase AC circuit?

Answer 18

Wattmeter

Question 19

What type of load is considered pure resistive in AC circuits?

Answer 19

Incandescent lamp (Conventional Bulb)

Question 20

What is the relationship between voltage and current in terms of phase angle in AC circuits?

Answer 20

The current I lags the applied voltage V by angle φ.

Question 21

What is the purpose of the observation tables in the experiments?

Answer 21

To record and compare theoretical and experimental values of currents and voltages.

Question 22

In Superposition Theorem, what happens to a voltage source when it is removed?

Answer 22

The terminals are short-circuited.

Question 23

In Superposition Theorem, what happens to a current source when it is removed?

Answer 23

The terminals are open-circuited.

Question 24

What is the procedure to verify Thevenin’s Theorem?

Answer 24

Measure load current with the original circuit and with the Thevenin equivalent circuit, then compare the values.

Question 25

What is the formula for calculating Active Power in a single phase A.C. circuit?

Answer 25

P = VI cos(Ø) ## Footnote Where P is Active Power, V is voltage, I is current, and Ø is the phase angle.

Question 26

What instruments are used to measure Active Power in a single phase A.C. circuit?

Answer 26

Wattmeters ## Footnote Wattmeters measure the Active Power based on the formula P = VI cos(Ø).

Question 27

What type of load is an incandescent lamp considered?

Answer 27

Pure resistive ## Footnote This is because its inductance and capacitance are negligible.

Question 28

How can the power factor of an unknown load be calculated?

Answer 28

cos(Ø) = P / VI ## Footnote Where P is the Active Power measured.

Question 29

What is the purpose of the observation table in the experiment?

Answer 29

To record readings of voltmeter, ammeter, and wattmeter ## Footnote This helps in calculating errors and analyzing power measurement.

Question 30

What is the efficiency formula for a transformer?

Answer 30

Efficiency = (W2 / W1) * 100 ## Footnote Where W2 is output power and W1 is input power.

Question 31

What types of losses occur in a practical transformer?

Answer 31

* Cu loss * Core/Iron loss ## Footnote These losses result in the output being less than the input power.

Question 32

What is the Open-Circuit test used for?

Answer 32

To determine core losses and no-load current ## Footnote It is performed with the secondary winding open.

Question 33

What is measured during the Short-Circuit test of a transformer?

Answer 33

Full load Cu loss ## Footnote This test is performed with the secondary winding short-circuited.

Question 34

What is the significance of the no-load current (I0) in a transformer?

Answer 34

It shows the core or iron losses ## Footnote The no-load current is typically very small, about 2% to 5% of the rated primary current.

Question 35

What is the core loss resistance formula?

Answer 35

Rc = V0 / I0 ## Footnote Where V0 is the voltage at open circuit and I0 is the no-load current.

Question 36

What is the relationship between Output Power and Input Power in a transformer?

Answer 36

Output Power = Input Power - Copper loss - Core loss ## Footnote This relationship is essential for calculating efficiency.

Question 37

What does the term 'Voltage Regulation' of a transformer refer to?

Answer 37

Percentage voltage regulation = ((E2 - V2) / V2) × 100 ## Footnote It indicates the change in voltage when the load varies.

Question 38

What is the purpose of using a variac in transformer testing?

Answer 38

To gradually change the supplied voltage ## Footnote This is necessary to reach the rated primary voltage of the transformer.

Question 39

What is a PN junction diode?

Answer 39

A two-terminal electronic device that allows current in only one direction ## Footnote Formed by doping semiconductors to create p-type and n-type regions.

Question 40

What condition allows current to flow in a forward-biased PN junction diode?

Answer 40

When the external voltage exceeds the potential barrier ## Footnote Approximately 0.7 volts for silicon and 0.3 volts for germanium.

Question 41

What is the depletion layer in a PN junction diode?

Answer 41

A region where no charge carriers are present ## Footnote Formed at the junction of p-type and n-type materials.

Question 42

What is the effect of applying a negative voltage to the N-type material in a forward-biased diode?

Answer 42

It repels electrons towards the junction ## Footnote This energy helps electrons cross the junction, allowing current flow.

Question 43

What is the forward bias condition of a PN junction diode?

Answer 43

When a negative voltage is applied to the N-type material and a positive voltage to the P-type material

Question 44

What occurs when the external voltage exceeds the potential barrier in a forward-biased diode?

Answer 44

Current starts to flow through the diode

Question 45

What is the knee voltage for silicon and germanium diodes?

Answer 45

* Silicon: approx. 0.7 volts * Germanium: approx. 0.3 volts

Question 46

What happens to a diode above the knee point in forward bias?

Answer 46

It effectively becomes a short circuit, allowing infinite current

Question 47

What is the reverse bias condition of a PN junction diode?

Answer 47

When a positive voltage is applied to the N-type material and a negative voltage to the P-type material

Question 48

What is the effect of reverse bias on the depletion layer of a PN junction diode?

Answer 48

The depletion layer grows wider due to a lack of electrons

Question 49

What is the typical current flow through a reverse-biased diode?

Answer 49

Practically zero current, with a very small leakage current in micro-amperes

Question 50

Fill in the blank: The characteristic curve of a forward-biased diode shows zero current until the _______.

Answer 50

knee voltage

Question 51

What apparatus is required to verify truth tables of basic gates?

Answer 51

Training board Model no NV6551 consisting of AND, OR, NOT, NAND, NOR, XOR, and XNOR gates

Question 52

What do electronic gates require to operate?

Answer 52

A power supply

Question 53

What are the two nominal values that represent logic 0 and logic 1 in electronic gates?

Answer 53

* 0V: Logic 0 * 5V: Logic 1

Question 54

What is a Zener diode?

Answer 54

A type of semiconductor diode that operates in the reverse breakdown region

Question 55

What is the Zener voltage?

Answer 55

The voltage at which a Zener diode allows current to flow in the reverse direction

Question 56

What are the applications of Zener diodes?

Answer 56

* Voltage regulation * Voltage reference applications

Question 57

What do De Morgan’s First Theorem state?

Answer 57

(A+B)’ = A’.B’

Question 58

What do De Morgan’s Second Theorem state?

Answer 58

(A.B)’ = A’+B’

Question 59

What is the principle of De Morgan's Theorems?

Answer 59

They allow negation of input variables and conversion from one form of Boolean function to an opposite form

Question 60

What is the significance of the output in a logic gate?

Answer 60

There is typically one output representing either logic 0 or logic 1

Question 61

True or False: De Morgan’s Theorems can be verified using truth tables.

Answer 61

True

Question 62

What is the difference between SOP and POS?

Question 63

What is the procedure to verify the truth table of logic gates?

Answer 63

Connect the circuit as per the diagram and note the outputs for all combinations of inputs