Mathskey.com - Recent questions and answers in ELECTRICAL ENGINEERING

Answered: AC Analysis

Fri, 12 Feb 2021 10:23:37 +0000

I know you may looking for a good professional writer to order a dissertation abstract international from him. I am the one who can help me.

Improper Integral - Fourier Transform Problem

Tue, 13 Oct 2020 12:00:50 +0000

Electrical engineering

Fri, 09 Mar 2018 22:25:40 +0000

Q1 two batteries having an EMF of 30 volt and 20 Volts and an internal resistance of 0.2 ohms and 1.2 ohms respectively are to be charged by a DC generator with an EMF or 40 volts and an internal resistance of 0.4 Ohms. use kirchhoffs law to calculate the value of the current 1.1.1supplied by the generator 1.1.2 through battery A 1.1.3 and through battery B

Electrical engineering

Fri, 09 Mar 2018 22:24:35 +0000

Q1 two batteries having an EMF of 30 volt and 20 Volts at an internal resistance of 0.2 ohms and 1.2 ohms respectively are to be charged by a DC generator with an EMF or 40 volts and an internal resistance of 0.4 Ohms. use kirchhoffs law to calculate the value of the current 1.1.1supplied by the generator 1.1.2 through battery A 1.1.3 and through battery B

voltage, power?

Fri, 25 Aug 2017 17:33:53 +0000

1.2

Two batteries of EMF 65 V and 50 V and internal resistance of 0,3 Ω and 0,6 Ω

respectively, are connected in parallel to supply a load resistance of 2,8 Ω.

Use Kirchhhoff’s laws to calculate the following:

1.2.1 The current supplied by each battery

1.2.2 The voltage across the load

1.3 The field coil of a motor has a resistance of 100 Ω at 250 C. By how much will the resistance increase if the motor attains a temperature of 1250 C when running. The temperature coefficient of resistance is 0,004 per degree C at 250 C

2.1 A coil with 2000 turns of conductor wire with total cross-sectional area of 200 mm2 and a mean length per turn of 200 mm, has an inductance of 4 Henry.

Calculate the following:

2.1.1 The resistance of the winding if the specific resistance of the conductor is 2 micro-ohm metres

2.1.2 The average value of the EMF induced in the coil when a current of 10 A is reversed (i.e. to -10 A) in 20 seconds

3.1 A resistor of unknown value R is connected in parallel with a resistance of 180 Ω. This combination is connected in series with a resistor of 25 Ω. The circuit is then connected across a 280 V DC supply.

Calculate the following

3.1.1. The value of the resistor R when a 4 A current is drawn from the supply

3.1.2. The power dissipated in the circuit

3.2 Two capacitors connected in series have respective volt readings of 90 V and 30 V. If the total charge equals 900 μC, calculate the following:

3.2.1. The total capacitance

3.2.2. The value of each capacitor

help with assignment school

Wed, 23 Aug 2017 15:45:54 +0000

1.2

Two batteries of EMF 65 V and 50 V and internal resistance of 0,3 Ω and 0,6 Ω

respectively, are connected in parallel to supply a load resistance of 2,8 Ω.

Use Kirchhhoff’s laws to calculate the following:

1.2.1 The current supplied by each battery

1.2.2 The voltage across the load

2.1 A coil with 2000 turns of conductor wire with total cross-sectional area of 200 mm2 and a mean length per turn of 200 mm, has an inductance of 4 Henry.

Calculate the following:

2.1.1 The resistance of the winding if the specific resistance of the conductor is 2 micro-ohm metres

2.1.2 The average value of the EMF induced in the coil when a current of 10 A is reversed (i.e. to -10 A) in 20 seconds

Calculate the following

3.1.1. The value of the resistor R when a 4 A current is drawn from the supply

3.1.2. The power dissipated in the circuit

3.2 Two capacitors connected in series have respective volt readings of 90 V and 30 V. If the total charge equals 900 μC, calculate the following:

3.2.1. The total capacitance

3.2.2. The value of each capacitor

Answered: help electrical prep for exam2

Thu, 04 May 2017 20:42:52 +0000

3.1

Match the tablular form.

Solution :

3.1.1 - A.

3.1.2- D.

3.1.3- C.

3.1.4- B.

help with revision for exams

Thu, 04 May 2017 19:21:36 +0000

1. use the superposition method to calculate the current through a 12 ohm resistor in figure 1:

2. refer to figure 2 and calculate the following:

2.1. I_A

2.2. Z_A

3.1. the following information is available for an LC π – filter circuit:

R_L=15kΩ

L=0,5H

Vdc=100V

V_r(rms)=10V

C₁=10µF

C₂=15µF

Rs=300Ω connected across the supply of 250V, 50Hz

Type = full-wave

Calculate the following:

3.1.1. the output ripple voltage

3.1.2. the output direct current voltage

3.1.3. the percentage ripple factor across the first capacitor

3.1.4. the percentage ripple factor across the second capacitor

3.2.1. TRUE OR FALSE? When a zener diode is used as a voltage regulator, it must be connected in forward bias.

3.2.2. TRUE OR FALSE? The tunnel diode can be used in high speed applications.

4.1. state five points that can be affected by negative feedback to improve the performance of a circuit.

4.2. draw a neat push-pull amplifier circuit which uses two NPN transistors. Clearly show the input and output waveforms.

4.3. state three applications of a uni-junction transistor.

4.4. an amplifier has a voltage gain of 50. If the input signal is 2mV, the value of the output voltage will be 0,01V. True Or False?

4.5. name three regions in which a transistor can operate.

4.6. Field effect transistor are (current/voltage/both) operated. Choose the correct answer.

5.1. using an input as a square wave, draw the output waveforms of the following operational amplifiers.

5.1.1. the intergrator

5.1.2. the non-inverter

5.1.3. the differentiator

5.1.4. the inverting

5.2. Give the name of an operational amplifier used without feedback.

6.1. Show with the aid of a neat, labelled diagram how a quadrac can be used to control the speed of a small AC motor. Also show the input and output waveforms.

6.2. Draw a neat, labelled block diagram of a closed-loop motor speed control.

6.3. Draw the characteristic curve of a light activated silicon controlled rectifier.

7.1. State three factors which influence the capacitance of capacitive transducer.

7.2. Draw and explain the operation of a transducer that is used to monitor the speed of rotation of a shaft.

8. an oscilloscope displays a sine wave over six vertical divisions and six horizontal divisions. The vertical amplifier is 2V per a division, and the time base is at 20 µs/division.

Calculate the following:

8.1. the amplitude

8.2. the peak to peak value

8.3. the frequency

8.4. the average DC value

1. A 12V battery is connected in series with an R₁=5Ω resistor. Two parallel resistors R₂ and R_L, with values 10 Ω and 8 Ω respectively are also included in the circuit. Use Kirchhoffs method to calculate the voltage drop across the load resistor R_L.

2. study the figure 1 and calculate the following:

2.1. the resonance frequency

2.2. the impedance of the circuit

2.3. the total current flow

2.4. Draw the phasor diagram

3. give one use of the following diodes:

3.1.1. the junction diode

3.1.2. the zener diode

3.1.3. the varactor diode

3.1.4. the tunnel diode

3.2. state three advantages of an LC filter

3.3. explain the term voltage regulation.

3.4. the following information is given for a capacitor filter.

- input = full wave rectifier

- frequency = 50Hz

- load current – 10mA

- capacitor value = 150µF

- maximum secondary voltage = 10 V

4.1. true or false

4.1.1. the common emitter amplifier produces at 0 deg C phase shift on the output.

4.1.2. in the FET the output current controls the input voltage

4.1.3. MOSFETs are widely used in digital applications

4.1.4. in an N-Channel JFET the majority carriers are electrons

4.1.5. UJT is a transistor with two

4.2. explain by means of a neat, labelled block diagram what you understand by negative feedback in amplifiers.

4.3. calculate the values of I_C and R_B if the following information is given:

- V_CC=10V

- V_be=0,6V

- R_C=1kΩ

- R_in=0,12MΩ

- B = 200

5.1. state four properties of an operational amplifier.

5.2. calculate the input voltage of an operational amplifier whose output voltage is in phase with input voltage, if the following information is available.

- ouput voltage = 4V

- Feedback resistance = 10kΩ

- Input resistance=1kΩ

Also draw the circuit diagram of this amplifier

5.3. draw the symbol, input and output wave forms of a comparator.

6.1. name three methods that can be used to switch off an SCR.

6.2. Demonstrate, with the aid of a labelled characteristic curve, the principle of operation of the following thyristors:

6.2.1. QUADRAC

6.2.2. LASCR

6.3. match each of the following:

	Column A		Column B
6.3.1.	Triac	A	A multilayer, three-terminal, bi-directional, semi-conductor device
6.3.2.	Diac	B	A four layer p-n-p-n device
6.3.3.	Scr	C	Basically a triac and diac combined together in a single package
6.3.4.	Lascr	D	A bi-directional trigger diode used as an AC Switch
6.3.5.	quadrac	E	A four-layer, p-n-p-n device turned on by light

6.4. boiling water in a kettle is an example of a open-loop system. Only state True or False.

7.1. explain, with the aid of a labelled sketch, how the pressure of a process can be observed by means of a differential transformer transducer.

7.2. name four points that should be considered before a transducer is selected for a particular application.

8. for the wave-form shown in figure 2, the amplifier gain setting is 0,6 V/div and the time-base setting is 2µsec/div.

Calculate the following:

8.1. the amplitude

8.2. the peak-to-peak value

8.3. the period

8.4. the frequency

8.5. the RMS value

help with revision for exams

Thu, 04 May 2017 19:14:25 +0000

1.1. Two batteries having an emf of 50V and 30V, an internal resistance of 0,4ohms and 1,2 ohms respectively are to be charged by a generator having an EMF of 60V and an internal resistance of 0,2ohms.

Use kirchoff’s law to determine the following:

1.1.1. the value of current supplied by the generator

1.1.2. the value of the current through battery A

1.1.3. the value of the current through batter B.

1.2. a 50 ohm resistor is connected across a rheostat which is then connected in series with a heater element of 500W. What must the value of the rheostat be so that the heater draws 10A when the whole circuit is connected across a 150V supply?

1.3. On what does the magnitude of the hysteresis loss depends?

1.4. what is the reason that certain alloys are used in the manufacturing of standard resistors for the use in measuring instruments?

2.1. two capacitors of 10 microfarads and 15 microfarads respectively, are connected in series across a 30V supply.

Calculate the following:

2.1.1. the total capacitance

2.1.2. the pd across each capacitor

2.2. State Lenz Law.

2.3. an aluminium conductor 22m long is connected in parallel with a copper conductor, having the same length. When a current of 25A passed through the combination it is found that the current through the copper conductor is 15A. the diameter of the aluminium is 4mm.

Calculate the following:

2.3.1. Diameter odf copper conductor if the resistivity of copper is 0,017 micro-ohm meters and that of the aluminium is 0,028 micr-ohm meters.

2.3.2. voltage drop across the conductors

2.4. the resistance of a coil of wire increases from 125 ohms at 50 deg C to 250 ohms at 300 deg C. Find the temperature co-efficient of the conductor.

3.1. the open circuit characteristics of a separately excited DC-Generator are given as follows:

Terminal voltage (V)	4	8	13	15,5	16	16,5
Field Current (A)	0,2	0,4	0,9	1,7	2,0	2,4

Plot a graph to determine the following:

3.1.1. the voltage to which the machine will excite on no-load when shunt-connected and the total field resistance is 8 ohms

3.1.2. the value of the critical resistance

3.2. a short shunt compound generator supplies a load current of 50A. it has a shunt filed resistance of 11 ohms, an armature resistance of 0,1 ohms and a field resistance of 0,2ohms.

Calculate the armature EMF, if the terminal voltage is 100V.

3.3. how can the field coils of DC machines be connected with self-excitation?

3.4. What is the chief purpose of a DC motor starter?

4.1. a single phase 13 320/1 332V, 60Hz transformer has a net area of 50cm² and a maximum flux density of 1 Tesla. Estimate the number of turns in each winding.

4.2. A sinusoidal AC supply has a maximum value of 400V and a frequency of 50Hz.

Calculate the following:

4.2.1. the RMS value of the voltage

4.2.2. the periodic time in milliseconds.

4.3. in a certain circuit of THREE parallel branches, the instantaneous branch currents are represented by:

4.3.1. calculate the magnitude of the supply current and write it in the form:

4.3.2. represent these currents by drawing a phasor diagram

4.4. an impedance of -3 –j3 ohms and an impedance of 6+j6 ohms are connected in series across a 240V, 50Hz supply.

Calculate the following:

4.4.1. the current flowing in the circuit

4.4.2. the power factor of the circuit

5.1. a 230V DC supply is connected across a circuit of 300 ohms resistor in series with a resistor of unknown value. A Voltmeter having a resistance of 300ohms is connected across the 300 ohms resistor and shows a reading of 30 Volt. Calculate the value of the unknown resistor.

5.2. what is the function of a Buchholz device on a transformer?

5.3. what is the purpose of a capacitor in a single phase capacitor motor?

5.4. what crystals are commonly used in the breather of a transformer and what purpose do they serve?

5.5.1. Name two types of feeders used in transmission systems

5.5.2. in which system does failure of ONE interconnecting feeder interrupt the supply to any of the other substations?

5.6. an ideal 30kVA transformer has 1200 primary turns and 40 secondary turns. The primary windings is connected to a 3kV, 60Hz supply.

Calculate the following:

5.6.1. secondary voltage

5.6.2. value of the secondary current and the primary currents on full load.

5.6.3. Maximum core flux

1.1. two capacitors of 15 microfarads and 4 microfarads respectively are connected in series across a 10 volt supply.

Calculate the following:

1.1.1. the total capacitance

1.1.2. the pd across each capacitor

1.2. why are certain currents that circulate in transformer cores undesirable and what are they called?

1.3. an aluminium conductor, 1km long, is connected in parallel with a copper conductor, having the same length. When a current of 350A passed through the combination, it is found that the current through the copper conductor is 150A. the diameter of the aluminium is 3m.

Calculate the following:

1.3.1. the diameter of the copper conductor if the resistivity of copper is 0,018 micro-ohm meters and that of the aluminium is 0,028 micro-ohm meters.

1.3.2. the voltage drop across the conductors

1.4. the field coil of a motor has a resistance of 300 ohms at 30 deg C. by how much will the resistance increase if the motor reached a temperature of 40 deg C when running? Take the temperature coefficient of the resistance to be 0,004 per deg C at 30 deg C.

2.1. a DC generator of EMF 75V and an internal resistance of 0,5 ohms are connected in parallel with a battery of EMF of 41V and internal resistance of 0,3 ohms. The combination is used to supply a load having a resistance of 2,5 ohms.

Use kirchhoffs law to determine the following:

2.1.1. the value and direction of the current through the generator

2.1.2. the value and direction of the current through the battery

2.1.3. the terminal voltage across the load

2.3. define the ampere.

2.4. what is the reason that certain alloys are used in the manufacturing of standard resistors for the use in measuring instruments?

3.1. the open circuit characteristics of a separately excited DC-Generator are given as follows:

Field Current (A)	10	20	30	40	85	100	120
EMF (V)	200	400	500	600	775	800	825

Plot a graph to determine the following:

3.1.1. the voltage to which the machine will excite on no-load when a shunt connected if the total field resistance is 8 ohms

3.1.2. the value of the critical resistance

3.2. a short shunt compound generator supplies a load current of 80A. it has a shunt resistance of 40 ohms, an armature resistance of 0,2 ohms and a field resistance of 0,5 ohms.

Calculate the armature EMF if the terminal voltage is 360 V.

3.3. name threes methods that can be used to overcome the effects of armature reaction.

3.4. what is the chief purpose of a DC motor starter?

4.1. a single phase 222/2 220V, 50 Hz transformer has an area of 100sm² and 200 turns on the primary windings. Calculate the maximum flux density in Tesla and the number of turns in the secondary windings.

4.2. a sinusoidal AC supply has a RMS value of 197,96 V and a periodic time of 30 milliseconds.

Calculate the following:

4.2.1. the maximum value of the voltage

4.2.2. the frequency of the supply.

4.3. in a certain circuit of THREE parallel branches, the instantaneous branch currents are represented by:

4.3.1. calculate the magnitude of the supply current and write it in the form:

4.4. an impedance of 15+j10 ohms and an impedance of 15-j10 ohms are connected in parallel across a 270, 825V, 50 Hz supply.

Calculate the following:

4.4.1. the total impedance of the circuit

4.4.2. the total current

4.4.3. the current in each branch

4.4.4. the total power

4.4.5. the power factor of the circuit

5.1. a single phase transformer has 20 secondary turns and 40 primary turns. The secondary winding is connected to a 200 Volt supply.

Calculate the following:

5.1.1. primary voltage

5.1.2 value of the primary current when the secondary current is 20A

5.1.3. primary power if the load has a power factor of 0,6.

5.2. name three types of capacitors

5.3. what is the purpose of the capacitor in a single phase capacitor motor

5.4. name two of the most common methods of cooling transformers

5.5. name two types of feeders used in transmission systems

5.6. a 400V DC supply is connected across a circuit of a 200 ohm resistor in series with a resistor of unknown value. A voltmeter having a resistance of 800 ohms is connected across the 200 ohm resistor and shows a reading of 200V.

Calculate the value of the unknown.

Electrical Engineering, Impedance

Sat, 10 Dec 2016 09:19:53 +0000

For my study guide I really need these two problems solved so that I know what I'm doing and can study right. Please help as quickly as possible if you can, thank you so much. Thanks!

1. The rms current through a 100 µH inductor is 10 mA when connected across a 6.3 V rms sinusoidal ac supply. Calculate the frequency of the ac supply. (Answer should be somewhere between 800 kHz and 1.2 MHz.)

2.The rms current through a 100 µF capacitor is 0.25 A when connected across a 4.0 V rms sinusoidal ac supply. Calculate the frequency of the ac supply. (Answer should be somewhere between 80 Hz and 120 Hz.)

Calculate the peak voltage

Sat, 19 Nov 2016 02:28:23 +0000

1.Calculate the peak voltage of a 60 Hz waveform if its instantaneous level is measured as 110 V at 2 ms from the instant of zero output. (Answer should be somewhere between 150 and 180 V.)

2. Determine the rms current in milliamps and average power dissipation in watts in a 330 Ω resistor with a 169.7 V peak sine wave applied across the resistor. (Answers should be somewhere between 350 and 380 mA for current and 30 to 50 W for power.)

3. A 297 Vrms sine wave is applied across a 3.9 kΩ resistor. Determine the following quantities regarding the resistor:

a) Ipeak. (Answer should be somewhere between 100 and 115 mA.)

b) Irms. (Answer should be somewhere between 60 and 90 mA.)

c) Pavg. (Answer should be somewhere between 10 and 30 W.)

4. A 120 Hz ac supply with a peak voltage of 100 V is applied across a 27 Ω resistor. Calculate the following values:

a) peak resistor current. (Answer should be somewhere between 3 and 4 A.)

b) rms resistor current. (Answer should be somewhere between 2 and 3 A.)

c) Average power dissipated in the resistor. (Answer should be somewhere between 170 and 200 W.)

Thevenin problem

Thu, 10 Nov 2016 15:01:02 +0000

AC Resonance

Wed, 20 Apr 2016 12:01:28 +0000

AC Resistance

Wed, 20 Apr 2016 11:47:45 +0000

Alternating Current

Wed, 20 Apr 2016 11:21:01 +0000

Circuit switch

Wed, 20 Apr 2016 11:15:59 +0000

AC Circuit Problem

Wed, 20 Apr 2016 09:42:40 +0000

AC Problem

Wed, 20 Apr 2016 09:10:00 +0000

AC Circuit

Tue, 29 Mar 2016 13:19:41 +0000

Resistor Problem

Mon, 21 Mar 2016 04:11:00 +0000

Problem Help

Mon, 21 Mar 2016 03:48:53 +0000

Problem Help

Sat, 19 Mar 2016 12:10:58 +0000

Answered: AC Circuit

Sat, 19 Dec 2015 20:01:06 +0000

(1)

Step 1:

Find the total impedance.

The inductive impedances are , and .

The mutual inductance are .

Find the total inductance at the coil 1:

Find the total inductance at the coil 2:

Find the total inductance at the coil 3:

Step 2:

Total impedance between the nodes and is .

is in series with .

Step 3:

Find the total current in the circuit.

Total current in the circuit is

Solution:

Total current in the circuit is

AC Thevenin Equivalent Circuit

Sat, 19 Dec 2015 14:59:05 +0000

Answered: AC Problem

Fri, 18 Dec 2015 16:59:19 +0000

Observe the circuit:

For delta networks: .

Find the phase currents.

Each line voltage is lag by .

The line currents are times the phase currents and lag by to their respective phase currents.

Phase currents are .

Line currents are .

AC Voltage

Fri, 18 Dec 2015 13:12:14 +0000

Answered: AC Effective Voltage

Thu, 17 Dec 2015 17:19:34 +0000

Step 1:

Use Superposition principle to calculate voltage across the resistor .

Super Position Theorem :

Take one current source at a time and replace all other with voltage with short or internal resistance and current sources with open.

The current flowing in the circuit is .

in polar form can be written as .

in complex form can be written as .

Apply current divider rule: .

Find the total impedance .

is in series with .

is in parallel to .

is in series with , and .

Current division rule:

Find the voltage drop across the resistor .

Step 2:

Take one voltage source at a time and replace all other with voltage with short or internal resistance and current sources with open.

The voltage in the circuit is .

in polar form can be written as .

in complex form can be written as .

Apply KVL to loop 1:

Find the voltage drop across the impedance .

Step 3:

By superposition principle :

The Voltage across the resistor is .

Voltage across the resistor is

Solution:

Voltage across the resistor is

Answered: AC Effective Current Problem

Thu, 17 Dec 2015 16:43:36 +0000

Observe the circuit:

in polar form can be written as .

in complex form can be written as .

Find the total impedance of the circuit.

and are in series

Find the current in the circuit.

AC Voltage Drop

Thu, 17 Dec 2015 12:31:11 +0000

AC Power

Thu, 17 Dec 2015 12:22:03 +0000

Answered: AC Effective Current

Wed, 16 Dec 2015 22:22:03 +0000

Step 1:

Observe the circuit:

The input sine voltage is .

in polar form can be written as .

in complex form can be written as .

Step 2:

Find the total impedance of the circuit.

and are in series.

Find the current in the circuit.

Current in series circuit is same.

Hence

in polar form can be written as

Solution:

Answered: AC Maximum Power

Wed, 16 Dec 2015 20:28:13 +0000

(1)

Maximum Power Transfer:

For any power source, the maximum power transferred from the power source to the load is when the resistance of the load is equal to the equivalent or input resistance of the power source .

Apply Thevinins theorem:

Find Thevinins equivalent impedance.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Impedance. This is the Thevenin Impedance ().

Redraw the circuit:

Observe the circuit:

can be written in complex form as .

can be written in polar form as

Answered: AC Problem Power

Wed, 16 Dec 2015 20:15:31 +0000

(b)

Step 1:

Find Thevenin's voltage.

Use Superposition principle to calculate volatge across A and B.

Super Position Theorem :

Take one current source at a time and replace all other with short or internal resistance.

in complex form can be written as .

Apply current divider rule: .

Find the total impdenace .

is in parallel to .

is in series to .

Current divider rule:

Find the voltage drop across the impedance Z.

Step 2:

Take another voltage source at a time and replace all other with open or internal resistance.

in complex form can be written as

Apply KVL to loop 1:

Find the voltage drop across the impedance Z.

Step 3:

By superposition principle :

The Voltage acoss the terminal A and B is .

Thevinins equivalent voltage is

Draw the equivalent circuit.

Power in the circuit is .

Power in the circuit is 17.89 W.

Solution:

Power in the circuit is 17.89 W.

Answered: AC Thevenin Problem

Wed, 16 Dec 2015 16:16:04 +0000

(1)

Step 1:

Find the Thevinins equivalent resistance.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Resistance. This is the Thevenin Resistance (R_TH).

Redraw the circuit:

Step 2:

Observe the circuit:

All the four impedances are in series.

can be written in complex form as .

can be written in polar form as .

Solution:

Answered: AC Thevenin

Wed, 16 Dec 2015 14:50:26 +0000

(1)

Step 1:

Find the Thevinins equivalent impedance.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Resistance. This is the Thevenin impedance (Z_TH).

Redraw the circuit :

Step 2:

Observe the circuit:

is in series with .

in polar form can be written as .

Solution:

Answered: AC Impedance Current

Tue, 15 Dec 2015 21:06:39 +0000

Step 1:

Millman states that the voltage at the ends of the circuit is given by

Where is the resistance at the voltage sources.

And is the resistance on the branch with no source or generators.

For the given circuit,

Voltage at the end of the nodes A and B is .

Find the Thevinins equivalent resistance of the circuit.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Resistance. This is the Thevenin Resistance (R_TH).

Redraw the circuit:

Step 2:

Observe the circuit:

can be written in complex form as .

Three impedances are in parallel.

Step 3:

Observe the circuit:

can be written in complex form as .

Substitute corresponding values in the millman's formula.

can be written in polar form as .

Voltage passes through each branch is .

Find the current passes resistor .

Solution:

Answered: AC Circuit

Tue, 15 Dec 2015 19:45:08 +0000

(1)

Step 1:

Millmans theorem:

Millman states that the voltage at the ends of the circuit is .

Where ,

is the resistance at the voltage sources and

is the resistance on the branch with no source or generators.

Find the Thevinins equivalent resistance of the circuit.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Resistance. This is the Thevenin Resistance (R_TH).

Redraw the circuit :

Step 2:

Observe the circuit:

can be written in complex form as

can be written in complex form as .

Three impedances are in parallel.

Step 3:

Observe the circuit:

can be written in complex form as .

Substitute corresponding values in the .

can be written in polar form as .

Solution:

Answered: AC Voltage Drop

Tue, 15 Dec 2015 17:44:45 +0000

Step 1:

Redraw the ciruit representing the current in the loop.

Apply KVL for the first loop:

Apply KVL for the second loop:

Step 2:

Substitute in equation (1).

Find the voltage across the resistor R.

in polar form can be written as .

Solution:

Answered: AC Max Power

Tue, 15 Dec 2015 15:18:17 +0000

(a)

Maximum Power Transfer:

For any power source, the maximum power transferred from the power source to the load is when the resistance of the load is equal to the equivalent or input resistance of the power source .

Apply Thevinin's theorem:

Find Thevinin's equivalent impedance.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Impedance. This is the Thevenin Impedance ().

Redraw the circuit:

Observe the circuit:

, and are in series.

Therefore, for maximum power transfer

AC Voltage

Tue, 15 Dec 2015 12:17:05 +0000

Answered: AC Circuit Problem

Mon, 14 Dec 2015 21:12:02 +0000

Step 1:

Millman's theorem:

Millman's theorem is applicable to a circuit which may contain only voltage sources in parallel or a mixture of voltage and current sources connected in parallel.

This theorem is nothing but a combination of Thevenins Theorem and Nortons Theorem.

Millman states that the voltage at the ends of the circuit is given by

Where is the resistance at the voltage sources.

And is the resistance on the branch with no source or generators.

For our circuit,

voltage at the end of the nodes A and B is .

Find the Thevinins equivalent resistance of the circuit.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Resistance. This is the Thevenin Resistance (R_TH).

Redraw the circuit :

Step 2:

Observe the circuit:

can be written in polar form as .

Three impedances are in parallel.

Step 3:

Observe the circuit:

can be written in polar form as .

Substitute corresponding values in the .

can be written in polar form as V.

Solution:

Answered: AC Thevenin

Mon, 14 Dec 2015 17:57:59 +0000

(2)

Step 1:

Find the thevinins equivalent voltage.

1.Open the load resistor.

2.Calculate the Open Circuit Voltage. This is the Thevenin Voltage (V_TH).

Use Superposition principle to calculate volatge across A and B.

Find the current through .

Super Position Theorem :

Take one voltage source at a time and replace all other with short or internal resistance.

in complex form can be written as .

Current in the circuit is .

Current in the circuit is

From (1): .

Voltage drop acoss : .

Step 2:

Take one voltage source at a time and replace all other with short or internal resistance.

in complex form can be written as .

Current in the circuit is .

Current in the circuit is

Voltage drop acoss : .

Step 3:

By superposition principle :

The Voltage acoss the terminal A and B is .

Thevinins equivalent voltage is

Solution:

Answered: Alternating Current

Mon, 14 Dec 2015 16:46:26 +0000

Observe the circuit:

The input voltage is .

and are in series.

and are in parallel.

Total impedance of the circuit is .

Find the current through the resistor .

Substitute and in .

can be written in polar form as .

Answered: AC Maximum Power

Mon, 14 Dec 2015 16:12:48 +0000

Step 1:

Maximum Power Transfer:

For any power source, the maximum power transferred from the power source to the load is when the resistance of the load is equal to the equivalent or input resistance of the power source .

Apply Thevinin's theorem:

Find Thevinin's equivalent impedance.

1.Open the load resistor.

2.Open Current Sources and Short Voltage Sources.

3.Calculate the Open Circuit Impedance. This is the Thevenin Impedance ().

Redraw the circuit:

Observe the circuit:

is in parallel with .

Step 2:

is in series with .

Convert the into polar form as .

Solution:

Answered: Power in AC Circuit

Sat, 12 Dec 2015 19:36:37 +0000

(b)

Step 1:

From (a):

Find the total current in the ciruit.

Step 2:

In a series network, current is same through each element.

Find the voltage drop across .

It is in the form of .

Here .

Find the power reading in wattmeter 2.

Solution:

Power in wattmeter 2 is

Answered: AC Circuit Resonance

Sat, 12 Dec 2015 17:01:55 +0000

(b)

From (a):

is in parallel to .

is in series with and .

Find the current.

Total current in the circuit at resonance is

Answered: AC Circuit

Sat, 12 Dec 2015 16:55:58 +0000

Observe the circuit:

The variable resistor is in parallel with .

If the circuit is at resonance then .

Therefore, .

Value of the variable resistor

Answered: AC Power

Sat, 12 Dec 2015 15:56:30 +0000

Step 1:

Observe the circuit:

Find the total impedance.

is in series with .

The input voltage is .

It is in the form of .

Here .

Step 2:

Voltage in a parallel network is same.

Find the power.

The power is .

Solution:

Answered: AC Circuit Power

Sat, 12 Dec 2015 15:29:10 +0000

Step 1:

Find the total impedance.

is in series with .

is in parallel to .

is in series with

Step 2:

The input voltage is .

It is in the form of .

Here .

Find the power.

Find the true power.

Solution:

True power is

Answered: AC Circuit Power

Fri, 11 Dec 2015 17:59:37 +0000

Step 1:

Find the total impedance.

is in series with .

is in parallel to .

is in series with

Step 2:

The input voltage is .

It is in the form of .

Here .

Find the power.

Find the true power.

Find the reactive power.

Find the apparent power.

Solution:

True power is 321.95 W.

Reactive power is 144.36 W.

Apparent power is 352.83 W.