Some of the Basic Concepts include :
1. Electric Current
The rate of flow of electric charge through any point of the circuit is called electric current. Its unit is ampere.
2. Coulomb's Law
According to this law, the force of attraction or repulsion between stationary point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
Where K = 9 X
Newton
Question for Basic Electrical Concepts
Try yourself:What is the unit of electric current?
Explanation
- Electric current is the rate of flow of electric charge through any point of the circuit.
- The unit of electric current is ampere (A).
- Ampere is a base unit in the International System of Units (SI) representing electric current.
- It is named after the French physicist Andr?-Marie Amp?re, who made significant contributions to the field of electromagnetism.
- Ampere is commonly used to measure the intensity of electric current in various electrical and electronic devices.
- In simple terms, it quantifies the amount of charge passing through a point in a circuit per unit time.
- Other units, such as milliampere (mA) and microampere (μA), are also used to express smaller values of electric current.
- Understanding the unit of electric current is essential for the proper measurement and analysis of electrical systems.
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3. Electric Field
It is the region surrounding an electric charge or group of charges, in which another charge experiences a force of attraction or repulsion.
4. Electric Lines of Forces
- An electric lines of force field along which a free isolated unit positive charge moves.
- Electric lines of force start from the positive charge and end to the negative charge.
- No two lines of force can intersect each other because if they do so, then at the point of intersection two tangents can be drawn which would mean two directions of force at that point which is impossible.
- These lines have a tendency to separate from each other in the direction perpendicular to their length.
- Lines of force of uniform field are parallel.
- Lines of force leaves the surface of the conductor normally.
Question for Basic Electrical Concepts
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What is the purpose of electric lines of force?Explanation
- Electric lines of force are used to represent the electric field around a charge or group of charges.
- These lines show the direction and strength of the electric field at different points in space.
- The purpose of electric lines of force is to indicate the force experienced by a positive test charge placed in the field.
- When the lines are closer together, it indicates a stronger electric field, and when they are farther apart, it represents a weaker field.
- The lines of force start from a positive charge and end on a negative charge, showing the direction of the force exerted on a positive test charge.
- The lines never intersect each other because it would imply multiple directions of force at a single point, which is not possible.
- In summary, electric lines of force help us visualize and understand the attraction or repulsion between charges in an electric field.
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5. Electric Flux
- It is defined as that total number of lines of force passing normally through a curved surface placed in the field or the dot product of and normal.
1 unit = Volt-meter
6. Ohm's Law
- According to this law if there is no charge the physical state of conductor (Such as temp.) then the current flowing through the conductor is directly proportional to the voltage applied i, e.
I α V .
I = - A graph between applied voltage and current is a straight line shows that it follows ohm's law.
- Ohm's law is valid for metallic conductors only.
7. Resistance
It is property of:
ρ = specific resistance or resistivity.
Note: The reciprocal of resistivity is called conductivity.
(Ohm – m)–1 = mho/meter.
Colour Code for Resistances:
- These resistances are usually carbon resistances and whose code is used to indicate the value of resistance.
- A carbon resistance has usually 4 concentric rings or bands A, B, C, D of different colours.
- The colour of first two bands A and B indicate the 1st two significant figures of resistance in ohms & those of 3rd band C indicate the decimal multiplies. The 4th band D (Which is either silver or gold) tells the tolerance.
- Sometimes only 3 colours band is there (A, B and C).
NOTE: B. ROY Great Britain Very Good Wife.
8. Electric Potential
- The electric potential at a point in an electric field is the ratio of the work done in bringing a test charge from infinity to that point to the magnitude of the test change.
- If the work done in moving a test charge q_{0} from infinity to that point against the field is W, then
9. Potential Gradient
Rate of charge of potential w.r.t distance in called potential gradient.
10. Electric Potential Energy
- The electric potential energy of a system of charges is the work that has to be done in bringing these charges from infinity to near each other to form the system.
- The potential energy of a system of charges q_{1} and q_{2} separated by a distance 'r' is
11. Capacitor
An element in which energy is stored in the form of an electrostatic field is called a capacitor.
Practical Capacitor
Capacitor Circuit diagram
12. Capacitance
Defined as the ratio of charge given to the plate of the capacitor to the potential difference produced between the plate.
Area of Plane
D → Distance between the planes.
∈_{0} = 8.85 x 10^{-12}
∈_{0} = Permittivitty of free space.
Unit – c^{2}N^{–1 }M^{–2}
For a capacitor, v ∝ q
Energy stored in a capacitor:
Energy(E) =
=
= C.
13. Inductor
It is an element in which energy is stored in the form of an electromagnetic field (Unit → Henry.)
Energy stored in Inductor:
= L.
Question for Basic Electrical Concepts
Try yourself:What is the unit of electric flux?
Explanation
- The unit of electric flux is given as volt-meter.
- Electric flux is defined as the total number of lines of force passing normally through a curved surface placed in the field or the dot product of electric field and normal.
- The unit of electric field is volt/meter and the unit of area is meter squared.
- Therefore, the product of the electric field and the area gives the unit of electric flux, which is volt-meter.
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14. Inductance
Inductance results from the fact that a flow of current produces a magnetic field, according to magnetic field along tends to induce a voltage (or current) in a wire according to Faraday's law.
(i) For RL Load :
V=V_{m} sin wt
show I lags by 90º R-L Load phasor :-
(ii) For RC Load:
Shows I leads by 90º
(iii) For RC phases:
(iv) For RLC Load:
Case 1: |V_{L}| > |V_{c}|
Case 2: |V_{L}| < |V_{c}|
Case 3: |V_{L}| = |V_{c}|
V = V_{R}
Ø = 0
CosØ = 1(UPF)
Note:- Reactive power is consumed by energy storing demands.