Gyrocompass, Gyroscope, Three Degree of Freedom, Properties of Gyroscopes


A gyrocompass is a type of non-magnetic compass which is based on a fast spinning disc and the rotation of the earth to find geographical direction automatically. Gyrocomapass are widely used for navigation purpose on ships.



The word Gyroscope derives from the Greek word ‘gyro’ means revolution and ‘skopics’ means to view. A gyroscope is a wheel or rotor mounted in two or three gimbals and pivoted supports that measure or maintain rotational motion or angular velocity by using earth gravity.

Three Degree of Freedom

  • Freedom to spin, rotation about the spin axis.
  • Freedom to turn in horizontal plane or freedom to turn about vertical axis.
  • Freedom to turn in vertical plane or freedom to turn about horizontal axis. Also described as freedom to tilt in altitude.

Or also can be described as

  • Freedom to spin : To spin about own axis, that is (X) axis.
  • Freedom to turn: To turn about vertical axis, that is (Y) axis.
  • Freedom to tilt: To tilt about horizontal axis, that is (Z) axis.

Properties of gyroscopes

Gyroscope have two basic properties

i. Rigidity in space

ii. Precession

  1. Rigidity in space: The axis of rotation (spin axis) of the gyro wheel tends to remain in a fixed dirction in space if no force is applied to it. It depands on the following factors-

i. Weight of the rotor

ii. Distribution of the weight

iii. Rotor speed

2. Precession: If external force is applied to the axis of rotation of a Gyro wheel , it works at 90 degree ahead of the direction of the applied force. It means if we try to tilt a gyro wheel, it will turn and if we try to turn it will tilt. This property is called precession. It depends on following factors

i. Angular momentum (spinning force)

ii. Applied force (Torque)

iii. Weight and shape of the rotor.

iv. Rotor speed

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Definition of Evil twins. Resistance-Conductance, Reactance-Susceptance, Impedance-Admittance, Inductive Reactance-Inductive Susceptance, Capacitive Reactance-Capacitive Susceptance, Inductance, Capacitance.

Resistance (R)

Resistance is the property of a conductor, which can oppose the flow of electricity. Resistance is inversely proportional to the flow of electricity.

That means the higher the resistance, the lower the current flow. Resistance depends upon,

Which substance opposes the movement of electrons among its atoms, then resistance is built upon that substance. The more easily the atoms give up and/or accept electrons, the lower the resistance.

Its unit is ohm and denoted by the Greek word Omega (Ω). German physicist George Simon Ohm (1784-1854) explained the relation between Voltage, Current, and Resistance. After that, the unit of resistance ohm was named according to his name. Ohms law was his popular formula. 

Fig: Resistors

All materials tend to resist electricity.  Some of them are lower, and some of them are more.

According to the amount of resistance of materials, they are broadly categorized into three

1. Conductor

2. Semiconductor 

3. Insulator

Conductance (G)

Conductance is the reciprocal of resistance. It’s also the property of a conductor, which allows to flow of electricity.
The standard unit of conductance is Siemens(S) and formerly known as mho. Its symbol is G.
When 1 amp current is passing through a component in the potential difference of 1Volt, then the conductance of that conductor is 1S (siemens). Conductance is directly proportional to the flow of electricity. If G is the conductance of the component, I is the passing current and V is the voltage across the component then the equation will be
And it is inversely proportional to the resistance. If the resistance is R (in ohm) and Conductance is G (in Siemens) then the equation is G=1/R

Symbol of Conductance

Reactance (X)

The combined opposition of inductance and capacitance of a circuit element(R-L circuit) to flow electricity is called reactance.
In other words, It is the opposition of a circuit element to the flow of current due to that element’s inductance or capacitance.
Reactance is denoted by X and its unit is the ohm (Ω). It is reciprocal of Susceptance.

Susceptance (B)

As there is reactance so too there is susceptance. As Resistance is the opposition of Conductance, the same Susceptance is the reciprocal (opposite) of Reactance. It is the property of a circuit (R-L) element that allows AC(changing)  current that flows through it. It is symbolized by B and measured in Siemens (S) same as conductance. 

The mathematical term can be expressed in… 


Impedances (Z)
The combined opposition of resistance and reactance (Inductive reactance + Capacitive reactance) of any electronic component, circuit, or system offers to alternating and/or direct electric current
is termed as Impedance.
The Impedance is denoted by Z and measured in ohm (Ω).

Impedance, Reactance & Resistance triangle
Impedance Graph

(Later Impedance will be describe broadly)

Admittance (Y)
Admittance is the property of a complex circuit or system (like an R-L-C circuit), which allows the flowing of alternating current(AC). It is a vector quantity consisting of two independent scalar quantities: Conductance(G) and Susceptance(B). It is the reciprocal of Impedance and symbolized by Y.
Admittance is the vector sum of conductance and susceptance. Susceptance is conventionally multiplied by the positive square root of -1, the unit imaginary number called symbolized by j, to express Y as a complex quantity G – jB L (when the net susceptance is inductive) or G + jB C (when the net susceptance is capacitive).
In parallel circuits, conductance and susceptance add together independently to yield the composite admittance. In series circuits, conductance and susceptance combine in a more

Fig 4.8 Admittance and Impedace triangle of parallel RLC circuit.

Inductive Reactance (XL)

The property of an inductor that opposes the flow of changing current is known as inductive reactance. Inductive reactance is usually related to the magnetic field surrounding a wire or a coil carrying current. It is directly proportional to the frequency. Higher frequency causes higher inductive reactance and lower frequency causes lower inductive reactance.

It is symbolized by (XL) and measured in ohms (Ω).

The mathematical formula is as follows

XL= 2πfL

Where XL= Inductive Reactance

f = Frequency

L = Inductance

Inductive Reactance

Inductive Susceptance (BL)

Inductive susceptance is like an evil twin of Inductive reactance. It is reciprocal of Inductive reactance. It is the property of an inductor that allows the changing current by not making a magnetic field around it.

It is denoted by BL, and the measuring unit is Siemens(S).


BL = 1/XL = 1/2πfL

Capacitive Reactance (XC)

The opposition offered by a capacitor to the flow of changing current is known as Capacitive Reactance. In a capacitor, the plates change potential difference or voltage. It is inversely proportional to the frequency and capacitance. That means as the frequency goes higher Capacitive reactance get lower and vice versa.

It is represented by XC and the measuring unit is ohm.

The mathematical formula is as follows

XC= 1/2πfC


XC= Capacitive Reactance

f = Frequency

C = Capacitance

Capacitive Reactance

Capacitive Susceptance (BC)

Capacitive susceptance is also like an evil twin of Capacitive reactance. It is reciprocal of Capacitive reactance. It is the property of a capacitor that allows the changing current (AC) by not changing potential difference or voltage.

It is denoted by BC, and the measuring unit is Siemens(S).


BC = 1/XC = 2πfC


Inductance is the property of an inductor that can oppose the changing current and produce a magnetic field. It can be also defined as the ratio of the induced voltage to the rate of change current causing it. Its SI unit is Henry(H) and denoted by ‘L’.

In SI base units: kg⋅m2⋅s−2⋅A−2

Derivations from other quantities: L = V / (I / t); L = Φ / I

Dimension: M1·L2·T−2·I−2



Capacitance is the capability to store electrical energy. Nearly all substances store electrical energy. It happened when positive and negative charges are separated, the stored electrical energy increases. It is a stored charge on a conductor or substance with a certain amount of potential difference.

Capacitance is symbolized by C and measuring unit is Farad(F).

Other units: μF, nF, pF

In SI base units: F = A2 s4 kg−1 m−2

Derivations from other quantities: C = charge / voltage

Dimension: M−1 L−2 T4 I2


What is Electrical Load? How many types of electrical load?

A device or equipment or component that consumes electrical energy and convert it into something useful energy such as heat, light, mechanical or rotating energy is considered as electrical load.

There are three types of electrical load.

1. Resistive Load

2. Inductive Load

3. Capacitive Load

1. Resistive load: In general the loads which are consists of any heating element that convert electrical energy into heating energy are known as resistive load. Such as heater, toaster, oven, etc are classified as resistive load. Resistive load obstruct flow of current and convert it into thermal energy. Resistive load consume power in such a way where voltage and current in- phase.Thus the power factor is unity(1). Its unit is ohm (Ω).

Fig: A simple Resistive circuit.
Fig: Voltage-Current waveform in resistive load.
Fig: A resistive load (Heater)

2.Inductive load: All electrical load that have a coil of wire and produce magnetic field are considered as inductive load. The voltage waveform of inductive load lagging behind the current wave. Thus the power factor of inductive load is lagging. The example of inductive loads are all types of motor, transformer, washing machine, vacuum cleaner, etc. Its unit is Henry(H).

Fig: Simple Inductive circuit.
Fig: Voltage-Current waveform in inductive load.
Fig: An Inductive load(motor)

3.Capacitive load: All kinds of capacitor are classified as capacitive load. In capacitive load the voltage wave lead the current wave. Thus the power factor of capacitive load is leading. The capacitors are useful in large circuit. When the inductive load, increases the cost of given power to offset the cost, drain capacitors are used. They are often included to power system to improve the overall power factor of the system. Examples are all capacitors, Power Bank, TV picture tube, capacitors which are used in single phase motor, etc. It’s unit is Farad (F).

Fig: A capacitive circuit
Fig: Voltage-Current waveform in capacitive load.
Fig: capacitive loads (capacitor bank)

What is AVR? Function of AVR. What happened if AVR fail? How to adjust an AVR?

1. What is AVR ?

An Automatic Voltage Regulator is an electronic device for automatically maintaining generator output terminal voltage at a set value under varying load
and operating temperature. It controls output by sensing the voltage V(out) at a power-generating coil and comparing it to a stable reference. The error signal is then used to adjust an average and value of the field current.

2. Function of AVR

Automatic voltage regulator helps to provide energy in exciter of a generator. The AVR components of your. Genset’s main function is to assert and sustain the appropriate voltage level range for your generator.

Automatic voltage regulator is a device which maintains the generator output terminal voltage. To be more accurate, AVR is a controller which always compares the generator output terminal voltage V(t) with the set reference voltage V(ref) and as per signal i.e. (Vref – Vt) it changes the field excitation of generator to maintain constant terminal voltage.

3. What happens if AVR fails?

When AVR fails, a protection called field failure protection will comes into picture and trip the generator. If failure of field is associated with under voltage which might happen due to severe fault near the generator and unable to maintain
the voltage, then the generator tripped instantaneously.

4. How do you adjust AVR?

With a flat head screw driver, turn the jeweler screw counter clockwise, this will lower the voltage. As screw is turned back, watch the voltmeter to see the desired adjustment. Keep doing  the adjustment until reach to the desired voltage.

Adjusting AVR with screw driver

Voltage, Current, Resistance?

Definition of voltage, current, resistance.
State of ohm’s law.


The potential difference between two points on a circuit, where one point has a greater charge than another point, this difference in charge between two points is called voltage. It’s measured in volt(V). The unit “volt” is named after the Italian physicist Alessandro Volta who invented what is considered the first chemical battery.

Consider a water tank to understand voltage.

The water is the charge, water pressure is the voltage, and the flow of water is the current.

If we think the battery is an water tank, where a certain amount of energy stored. As the water released by the hose, the pressure will go down. So it can be considered as decreasing voltage as we see light gone dimmer when battery low.

Voltage is like the pressure created by the water.
what is voltage?


In a word, the current is the flow of electrons due to the potential difference of two-point.

We can think of the amount of water flowing through the hose from the tank as current. The higher the pressure, the higher the flow, and vice-versa. With water, we would measure the volume of the water flowing through the hose over a certain period of time. With electricity, we measure the amount of charge flowing through the circuit over a period of time. Current is measured in Amperes (usually just referred to as “Amps”). An ampere is defined as 6.241*10^18 electrons (1 Coulomb) per second passing through a point in a circuit. Amps are represented in equations by the letter “I”.

Let’s say now that we have two tanks, each with a hose coming from the bottom. Each tank has the exact same amount of water, but the hose on one tank is narrower than the hose on the other.


The property of a conductor that can oppose the flow of electricity is called resistance. It is the basic property of a conductor and almost every substance has resistivity. Relation between current and resistance is inversely proportional. Higher resistance conductor allow less current flow.

The unit of resistance is ohm “Ω”.

This brings us back to Georg Ohm. Ohm defines the unit of resistance of “1 Ohm” as the resistance between two points in a conductor where the application of 1 volt will push 1 ampere, or 6.241×10^18 electrons. This value is usually represented in schematics with the greek letter “Ω”, which is called omega, and pronounced “ohm”.

Ohm’s Law

Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

Combining the elements of voltage, current, and resistance, Ohm developed the formula:

alt text


V = Voltage in volts

I = Current in amps

R = Resistance in ohms