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Mechanics and E&M cheat sheet, Cheat Sheet of Electric Machines

A useful and handy guide, of all the equations one may need in first year Electricity and magnitism

Typology: Cheat Sheet

2019/2020

Uploaded on 10/16/2021

tajbir-randhawa
tajbir-randhawa 🇨🇦

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Displacement
Δ𝑥=𝑥𝑥0
𝑟=𝑟𝑟0
Constant velocity
𝑣𝑥=Δ𝑥
Δ𝑡
𝑣𝑥= lim
Δ𝑡→0Δ𝑥
Δ𝑡=d𝑥
d𝑡
Acceleration
𝑎𝑥=𝛥𝑣𝑥
Δ𝑡
𝑎𝑥= lim
Δ𝑡→0Δ𝑣𝑥
Δ𝑡 =d𝑣𝑥
d𝑡
Relative velocity
𝑣𝑥𝑨𝑹=𝑣𝑥𝑨𝑩+𝑣𝑥𝑩𝑹
𝑣𝑥𝑨𝑩=−𝑣𝑥𝑩𝑨
Uniformly accelerated
movement
𝑣𝑥=𝑣𝑥0+𝑎𝑥𝑡
Δ𝑥=𝑣𝑥𝑜𝑡+1
2𝑎𝑥𝑡2
Δ𝑥=𝑣𝑥0+𝑣𝑥
2𝑡
𝑣𝑥2=𝑣𝑥0
2+2𝑎Δ𝑥
Period and frequency
𝑇=2𝜋𝑟
𝑣
𝑓=1
𝑇
Centripetal
acceleration
𝑎𝐶=𝑣2
𝑟𝑟
Laws of motion
𝐹𝑖=𝑚𝑎
𝒊
𝐹𝐴 sur B=−𝐹𝐵 sur A
Density
𝜌=𝑚
𝑉
Gravitational force
𝐹𝑔=𝐺𝑚1𝑚2
𝑟2𝑟
𝐹𝑔=𝑚𝑔
𝑔=𝐺𝑚
𝑟2
Force of a spring
𝐹𝑠=𝑘|Δ𝑙| 𝑢
Δ𝑙=𝐿𝐿𝑛𝑎𝑡
Friction
𝑓𝑐=𝜇𝑐|𝑁
󰇍
󰇍
|𝑢
0𝑓𝑠𝜇𝑠|𝑁
󰇍
󰇍
|𝑢
Archimedes’ equation
𝐹𝐴=−𝜌𝑓𝑉𝑔
Pressure
𝑃
󰇍
=𝐹
𝐴𝑢
𝑃
𝐵=𝑃𝑆
󰇍
󰇍
󰇍
+𝜌𝑔ℎ
Work
𝑊=𝐹𝑟
𝑊=𝐹𝑥Δ𝑥+𝐹𝑦Δ𝑦+𝐹𝑧Δ𝑧
Kinetic energy
𝐾=1
2𝑚𝑣2
Energy of spring
𝑈𝑠=1
2𝑘Δ𝑙2
Energy potential of
gravity
𝑈𝑔=𝑚𝑔
𝑈𝑔=𝐺𝑚1𝑚2
𝑟
Energy conservation
𝐸=𝐾+𝑈
𝐸𝑓=𝐸𝑖+𝑊𝑛𝑐
d𝐸
d𝑡=0
Exit speed
𝑣𝑒𝑥𝑖𝑡=2𝐺𝑚
𝑟
Power
𝑃=𝑊
Δ𝑡
𝑃=𝐹𝑣
Momentum
𝑝=𝑚𝑣
𝐹=Δ𝑝
Δ𝑡
Uniformly accelerated
rotation
𝜔=𝜔0+𝛼𝑡
Δ𝜃=𝜔0𝑡+1
2𝛼𝑡2
Δ𝜃=𝜔0+𝜔
2𝑡
𝜔2=𝜔0
2+2𝛼Δ𝜃
Relation between
angular parameters
𝑥=𝑟𝜃
𝑣𝑥=𝑟𝜔
𝑎𝑥=𝑟𝛼
Centripetal
acceleration
𝑎𝑐=𝑟𝜔2
Torque
𝜏=𝑟×𝐹
Equilibrium
𝐹𝑖=0
󰇍
𝒊
𝜏𝑖=0
𝒊
Center of mass
𝑟𝐶𝑀 =𝑚𝑖𝑟𝑖𝑖
𝑚𝑖𝑖
Kinetic energy of
rotation
𝐾=1
2𝐼𝜔2
𝐾=1
2𝐼𝐶𝑀𝜔2+1
2𝑚𝑣𝐶𝑀
2
Inertia
Particle: 𝐼𝐶𝑀=𝑚𝑟2
Cylinder: 𝐼𝐶𝑀=1
2𝑚𝑟2
Sphere: 𝐼𝐶𝑀=2
5𝑚𝑟2
Shell: 𝐼𝐶𝑀=2
3𝑚𝑟2
Rod: 𝐼𝐶𝑀=1
12𝑚𝑟2
Rod: 𝐼𝑒𝑥𝑡𝑟𝑒𝑚𝑖.=1
3𝑚𝑟2
Work and power of
rotation
𝑊=𝜏Δ𝜃
𝑃=𝜏𝜔
Dynamic of rotation
𝜏
𝑖=𝐼𝛼
Kinetic momentum
𝐿
󰇍
=𝐼𝜔
󰇍
󰇍
𝐿
󰇍
= 𝑟 × 𝑝
Numerical values
𝑔 =9.8 m/s2
𝐺=6.671011Nm2
kg2
𝑃𝑎𝑡𝑚 =101.3 kPa
Quadratic equation
𝑎𝑥2+𝑏𝑥+𝑐=0
𝑥1,2=−𝑏±𝑏24𝑎𝑐
2𝑎
Circle
𝐶=2𝜋𝑟
𝐴=𝜋𝑟2
Sphere
𝐴=4𝜋𝑟2
𝑉=4
3𝜋𝑟3
Trigonometry
𝑆𝑂𝐻𝐶𝐴𝐻𝑇𝑂𝐴
𝐻2=𝐴2+𝑂2
sin2𝜃+cos2𝜃=1
sin2𝜃=2sin𝜃cos𝜃
sin𝛼
𝐴=sin𝛽
𝐵=sin𝛾
𝐶
𝐶2=𝐴2+𝐵22𝐴𝐵cos𝛾
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Displacement

0

0

Constant velocity

𝑥

𝑥

= lim

Δ𝑡→ 0

d𝑥

d𝑡

Acceleration

𝑥

𝑥

𝑥

= lim

Δ𝑡→ 0

𝑥

d𝑣

𝑥

d𝑡

Relative velocity

𝑥𝑨𝑹

𝑥𝑨𝑩

𝑥𝑩𝑹

𝑥𝑨𝑩

𝑥𝑩𝑨

Uniformly accelerated

movement

𝑥

𝑥 0

𝑥

𝑥𝑜

𝑥

2

𝑥 0

𝑥

𝑥

2

𝑥 0

2

Period and frequency

Centripetal

acceleration

𝐶

2

Laws of motion

𝑖

𝒊

𝐴 sur B

𝐵 sur A

Density

Gravitational force

𝑔

1

2

2

𝑔

2

Force of a spring

𝑠

𝑛𝑎𝑡

Friction

𝑐

𝑐

𝑠

𝑠

Archimedes’ equation

𝐴

𝑓

Pressure

𝐵

𝑆

Work

𝑊 = 𝐹

𝑥

Δ𝑥 + 𝐹

𝑦

Δ𝑦 + 𝐹

𝑧

Δ𝑧

Kinetic energy

2

Energy of spring

𝑠

2

Energy potential of

gravity

𝑔

𝑔

1

2

Energy conservation

𝑓

𝑖

𝑛𝑐

d𝐸

d𝑡

Exit speed

𝑒𝑥𝑖𝑡

Power

Momentum

Uniformly accelerated

rotation

0

0

2

0

2

0

2

Relation between

angular parameters

𝑥

𝑥

Centripetal

acceleration

𝑐

2

Torque

𝜏⃗ = 𝑟⃗ × 𝐹

Equilibrium

𝑖

𝒊

𝑖

𝒊

Center of mass

𝐶𝑀

𝑖

𝑖 𝑖

𝑖 𝑖

Kinetic energy of

rotation

2

𝐶𝑀

2

𝐶𝑀

2

Inertia

Particle: 𝐼

𝐶𝑀

2

Cylinder: 𝐼

𝐶𝑀

2

Sphere: 𝐼

𝐶𝑀

2

Shell: 𝐼

𝐶𝑀

2

Rod: 𝐼

𝐶𝑀

2

Rod: 𝐼

𝑒𝑥𝑡𝑟𝑒𝑚𝑖.

2

Work and power of

rotation

Dynamic of rotation

𝑖

Kinetic momentum

= 𝑟⃗ × 𝑝⃗

Numerical values

𝑔 = 9. 8 m/s

2

− 11

N ⋅ m

2

kg

2

𝑎𝑡𝑚

= 101. 3 kPa

Quadratic equation

2

1 , 2

2

Circle

2

Sphere

2

3

Trigonometry

2

2

2

sin

2

𝜃 + cos

2

sin 2 𝜃 = 2 sin 𝜃 cos 𝜃

sin 𝛼

sin 𝛽

sin 𝛾

𝐶

2

= 𝐴

2

  • 𝐵

2

− 2 𝐴𝐵 cos 𝛾

Coulomb Law

12

1

2

2

12

21

Principle of superposition

(force)

1

1 𝑖

𝑖

Electric force

𝐸

Electric field

2

Principle of superposition

(field)

𝑝

𝑝𝑖

𝑖

Electric flux (plane

surface and uniform

field)

E

Electric flux

𝐸

Integrals

Gauss theorem

𝑛𝑒𝑡

0

Density of charge

1 D: 𝑄 = 𝜆 ⋅ 𝑙

2 D: 𝑄 = 𝜎 ⋅ 𝐴

3 D: 𝑄 = 𝜌 ⋅ 𝑉

Conservation of energy

𝑜𝑢𝑡

Potential energy of

electric potential

𝐸

General equation of

potential

Electric potential in

uniform electric field

Electric potential of a

point charge

𝑖

𝑖

𝑖

Potential energy of a

point charge system

𝑖

𝑗

𝑖𝑗

𝑖<𝑗

Equation of capacitance

Capacity of ONLY plane

capacitor

0

Equivalent capacity

(parallel)

𝑒𝑞

𝑖

𝑖

Equivalent capacity

(series)

𝑒𝑞

𝑖

𝑖

Potential energy stored

in a capacitor

𝐸

2

𝐸

2

𝐸

Ohm Law

Electric Power

2

Kirchhoff Law

𝑘

𝑘

= 0 A

𝑘

𝑘

= 0V

Equivalent resistance

(parallel)

𝑒𝑞

𝑖

𝑖

Equivalent resistance

(series)

𝑒𝑞

𝑖

𝑖

Magnetic force on a

moving particle

= 𝑞𝑣⃗ × 𝐵

Magnetic force due to a

current carrying wire

× 𝐵

Magnetic torque

Total torque

𝜏⃗ = 𝜇⃗ × 𝐵

Magnetic field of a wire

0

Magnetic field on the axis

of a loop

0

𝑁𝐼 sin

3

Magnetic field on the axis

of a solenoid (not

infinite)

𝐵 =

𝜇

0

𝑛𝐼

2

(cos 𝛼

2

− cos 𝛼

1

)

Magnetic field inside an

infinite solenoid

0

Theorem of Ampere

0

𝑛𝑒𝑡

Magnetic flux

𝐵

= 𝐵𝐴 cos 𝜃

𝐵

Electromotive force

𝐵

𝐵

Law of reflection

Law of Snell-Descartes

1

sin 𝜃

1

2

sin 𝜃

2

Total internal reflection

1

sin 𝜃

𝑐𝑟𝑖𝑡

2

Spherical mirror

𝑖

𝑜

One-sided lenses

1

2

2

1

𝑖

𝑜

1

2

Two-sided lenses

2

1

1

1

2

𝑖

𝑜

Interference

𝛿 = 𝑚𝜆 or 𝑚 2 𝜋

𝛿 = (𝑚 +

1

2

) 𝜆 or

( 2 𝑚 + 1

) 𝜋

𝛿 ≈ 𝑑 sin 𝜃

sin 𝜃 ≈ tan 𝜃 =

Frequency vs speed

Thin film

𝐸𝐷

𝐵

𝐴

𝐸𝐷

𝑓

and 𝛿 ≈ 2 𝑒

𝑓

0

𝑓

Cross product

𝐴

× 𝐵

⃗⃗

= |

𝑥̂ 𝑦̂ 𝑧̂

𝑎

𝑥

𝑎

𝑦

𝑎

𝑧

𝑏 𝑥

𝑏 𝑦

𝑏 𝑧

|

Numerical values

𝑘 = 8. 99 ⋅ 10

9

N ⋅ m

2

C

2

𝜖

0

= 8. 85 ⋅ 10

− 12

C

2

N ⋅ m

2

𝑒 = 1. 602 ⋅ 10

− 19

C

𝑚 𝑝

= 1. 67 ⋅ 10

− 27

kg

𝑚 𝑒

= 9. 11 ⋅ 10

− 31

kg

𝑐 = 299 792 458

m

s

1 eV = 1. 602 ⋅ 10

− 19

J

𝜇 0

= 4 𝜋 ⋅ 10

− 7

Tm

A