Workshop Flashcards
What does Kirchhoff’s Current Law (KCL) state?
The algebraic sum of currents entering and leaving a node at any instant of time must be equal to zero.
What is the equation representing Kirchhoff’s Current Law?
I = I1 + I2 + I3
What does Kirchhoff’s Voltage Law (KVL) state?
In a closed circuit, the algebraic sum of all source voltages must be equal to the algebraic sum of all the voltage drops.
What is the equation representing Kirchhoff’s Voltage Law?
V = V1 + V2 + V3
What is Thevenin’s Theorem?
A complex, linear bilateral network can be replaced by a simple network containing a Voltage source Vth in series with a resistance Rth.
What is the significance of Vth in Thevenin’s Theorem?
Vth is the open circuit voltage between the terminals from where the circuit is being replaced.
What does Rth represent in Thevenin’s Theorem?
Rth is the equivalent resistance between the terminals after replacing all sources by their internal resistances.
What is the principle of Superposition Theorem?
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.
What is true power in an AC circuit?
The power actually consumed in an AC circuit, also known as Real power or Active power.
How is Active power calculated?
P = V x I x cos(Ø)
What is Reactive power?
Power consumed in inductor and capacitor, calculated as Q = V x I x sin(Ø).
What does Apparent power represent?
Apparent power is given by S = VI volt-amperes (VA).
What is the formula for Reactive power?
Q = VI sin(Ø) volt-amperes reactive (VAR).
What is the definition of a node in electrical circuits?
A point in a circuit where two or more circuit elements are connected.
What is the difference between Electric network and Electric circuit?
An electric network is a combination of various components, while an electric circuit is a closed path through which current flows.
Fill in the blank: The algebraic sum of current meeting at a node is ______.
zero
True or False: KVL can be verified by measuring voltages across resistors in a closed loop.
True
What equipment is used to measure power in a single-phase AC circuit?
Wattmeter
What type of load is considered pure resistive in AC circuits?
Incandescent lamp (Conventional Bulb)
What is the relationship between voltage and current in terms of phase angle in AC circuits?
The current I lags the applied voltage V by angle φ.
What is the purpose of the observation tables in the experiments?
To record and compare theoretical and experimental values of currents and voltages.
In Superposition Theorem, what happens to a voltage source when it is removed?
The terminals are short-circuited.
In Superposition Theorem, what happens to a current source when it is removed?
The terminals are open-circuited.
What is the procedure to verify Thevenin’s Theorem?
Measure load current with the original circuit and with the Thevenin equivalent circuit, then compare the values.
What is the formula for calculating Active Power in a single phase A.C. circuit?
P = VI cos(Ø)
Where P is Active Power, V is voltage, I is current, and Ø is the phase angle.
What instruments are used to measure Active Power in a single phase A.C. circuit?
Wattmeters
Wattmeters measure the Active Power based on the formula P = VI cos(Ø).
What type of load is an incandescent lamp considered?
Pure resistive
This is because its inductance and capacitance are negligible.
How can the power factor of an unknown load be calculated?
cos(Ø) = P / VI
Where P is the Active Power measured.
What is the purpose of the observation table in the experiment?
To record readings of voltmeter, ammeter, and wattmeter
This helps in calculating errors and analyzing power measurement.
What is the efficiency formula for a transformer?
Efficiency = (W2 / W1) * 100
Where W2 is output power and W1 is input power.
What types of losses occur in a practical transformer?
- Cu loss
- Core/Iron loss
These losses result in the output being less than the input power.
What is the Open-Circuit test used for?
To determine core losses and no-load current
It is performed with the secondary winding open.
What is measured during the Short-Circuit test of a transformer?
Full load Cu loss
This test is performed with the secondary winding short-circuited.
What is the significance of the no-load current (I0) in a transformer?
It shows the core or iron losses
The no-load current is typically very small, about 2% to 5% of the rated primary current.
What is the core loss resistance formula?
Rc = V0 / I0
Where V0 is the voltage at open circuit and I0 is the no-load current.
What is the relationship between Output Power and Input Power in a transformer?
Output Power = Input Power - Copper loss - Core loss
This relationship is essential for calculating efficiency.
What does the term ‘Voltage Regulation’ of a transformer refer to?
Percentage voltage regulation = ((E2 - V2) / V2) × 100
It indicates the change in voltage when the load varies.
What is the purpose of using a variac in transformer testing?
To gradually change the supplied voltage
This is necessary to reach the rated primary voltage of the transformer.
What is a PN junction diode?
A two-terminal electronic device that allows current in only one direction
Formed by doping semiconductors to create p-type and n-type regions.
What condition allows current to flow in a forward-biased PN junction diode?
When the external voltage exceeds the potential barrier
Approximately 0.7 volts for silicon and 0.3 volts for germanium.
What is the depletion layer in a PN junction diode?
A region where no charge carriers are present
Formed at the junction of p-type and n-type materials.
What is the effect of applying a negative voltage to the N-type material in a forward-biased diode?
It repels electrons towards the junction
This energy helps electrons cross the junction, allowing current flow.
What is the forward bias condition of a PN junction diode?
When a negative voltage is applied to the N-type material and a positive voltage to the P-type material
What occurs when the external voltage exceeds the potential barrier in a forward-biased diode?
Current starts to flow through the diode
What is the knee voltage for silicon and germanium diodes?
- Silicon: approx. 0.7 volts
- Germanium: approx. 0.3 volts
What happens to a diode above the knee point in forward bias?
It effectively becomes a short circuit, allowing infinite current
What is the reverse bias condition of a PN junction diode?
When a positive voltage is applied to the N-type material and a negative voltage to the P-type material
What is the effect of reverse bias on the depletion layer of a PN junction diode?
The depletion layer grows wider due to a lack of electrons
What is the typical current flow through a reverse-biased diode?
Practically zero current, with a very small leakage current in micro-amperes
Fill in the blank: The characteristic curve of a forward-biased diode shows zero current until the _______.
knee voltage
What apparatus is required to verify truth tables of basic gates?
Training board Model no NV6551 consisting of AND, OR, NOT, NAND, NOR, XOR, and XNOR gates
What do electronic gates require to operate?
A power supply
What are the two nominal values that represent logic 0 and logic 1 in electronic gates?
- 0V: Logic 0
- 5V: Logic 1
What is a Zener diode?
A type of semiconductor diode that operates in the reverse breakdown region
What is the Zener voltage?
The voltage at which a Zener diode allows current to flow in the reverse direction
What are the applications of Zener diodes?
- Voltage regulation
- Voltage reference applications
What do De Morgan’s First Theorem state?
(A+B)’ = A’.B’
What do De Morgan’s Second Theorem state?
(A.B)’ = A’+B’
What is the principle of De Morgan’s Theorems?
They allow negation of input variables and conversion from one form of Boolean function to an opposite form
What is the significance of the output in a logic gate?
There is typically one output representing either logic 0 or logic 1
True or False: De Morgan’s Theorems can be verified using truth tables.
True
What is the difference between SOP and POS?
What is the procedure to verify the truth table of logic gates?
Connect the circuit as per the diagram and note the outputs for all combinations of inputs
