Marine Electrical Important Formulas for MEO Class 2

 1. Resistance

> V=IR or R=V/I

2. Law of resistance

> R= ρL/A

3. Resistance In series

> R=R1+R2+R3

> V=V1+V2+V3

> I=I1=I2=I3

4. Resistance In Parallel

> 1/R=1/R1+1/R2+1/R3

> I= I1+I2+I3

> Voltage Is Same v=V1=V2=V3

5. Capacitance

> C= q/V

q- Charge

V- Electric potential

> C=ε0A/d 

C- capacitance, in farads;

A- area of overlap of the two plates, in square meters

ε0- electric constant (ε0 ≈ 8.854×10−12 F⋅m−1)

d- separation between the plates, in meters;

6. Capacitors in series

>  1/C=1/C1+1/C2+1/C3

>  V=V1+V2+V3

> Charge is same q=q1=q2=q3

7. Capacitors are parallel

> C=C1+C2+C3

> q=q1+q2+q3

> Voltage is same V=V1=v2=v3

8. Inductor

> V=L *dI/dt

L- Inductance in Hentry

dI/dt- Rate of change of electric current in amp/sec

9. Inductors In Series

> L=L1+L2+L3

10. Inductors in Parallel

 > 1/L=1/L1+1/L2+1/L3

11. Impedance Z

 Impedance is a measure of the overall opposition of a circuit to current, in other words: how much the circuit impedes the flow of charge. It is like resistance, but it also takes into account the effects of capacitance and inductance. Impedance is measured in ohms (ohm).

> Impedance, Z = V/I


12. Reactance X

   Reactance (symbol X) is a measure of the opposition of capacitance and inductance to current. Reactance varies with the frequency of the electrical signal. Reactance is measured in ohms (ohm).

> Total Reactance, X = XL - Xc

> Capacitive Reactance, Xc = 1/2πfC

> Inductive Reactance, XL = 2pifL

Xc - reactance in ohms (ohm)

f    - frequency in hertz (Hz)

C  - capacitance in farads (F)

L   - inductance in henrys (H)

XL - reactance in ohms (ohm)

13. Resonant Frequency 

 In a series RLC circuit there becomes a frequency point were the inductive reactance of the inductor becomes equal in value to the capacitive reactance of the capacitor

> XL = XC

> Z = X

14. Phase Angle

 > cos φ = R/Z

15. Power 

> P= V I cos φ

> For resistance only circuit P= V I, Here Cos φ is One

16. RLC circuit

> f = 1 / [2π * √(L * C)]







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