Physics Course/Electricity

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Charged Particles

Charged Particles are the smallest indivisible charged carrying particles that make up Matter's Atom . There are three kinds of Charged Particles, namely the Electron, Proton and Neutron.

Charged Particles Mass Charge Notation
Electron 9.1094 × 10−31 kg −1.602 × 10−19 C e-
Proton 9.1094 × 10−31 kg +1.602 × 10−19 C p+
Neutron 1.6726 ×10-27 kg 0 C p0

Atom's Model

  1. All Matter posses a Mass and a Volume exist in three states Solid, Liquid, Gas
  2. All Matter are made from Chemical Element's Atom
  3. Atoms are made from Charged Particles
  4. Atom has a Nucleus consists of Proton and Neutron in the center with electrons on circular orbits circulate the Nucleus
  5. Only Electron on the outermost orbit has the capability to participate in electric reaction
  6. Electron on the outermost orbit has the highest Potential (Rest) Energy and lowest Kinetic Energy
  7. Each electron orbit or a shell has a quantum energy level, a distinct energy level
  8. There are four of these shells that has a quanta of Energy
  9. When an Electron moves from low energy to high energy level light will be emitted

Electric Charge

Normally all object has a net charge of zero. When an object give or receive electrons it will become Positivedly Charge or Nagatively Charge

Object + e- = Positive Charge
Object - e- = Negative Charge

All Charges have the following characteristics Electric Field , Magnetic Field and Electric Charge

Electric Field Lines.svg
Electric Charge Electric Field Lines Magnetic Field Lines Charge Quantity
Negative Charge -Q Point in Clock-wise direction
Positive Charge +Q Point Out Countered Clock-wise direction


When Electric charges interact with each other Electricity is generated . The interaction of Electric Charge to cause Electricity is either by

  1. Attraction of two different charges . - <-- + . + --> -
  2. Differences in Charges' quantity . ++++ --> ++

The first is called Kinetic Energy The second is called The Potential Energy

ElectroMagnetic Force

Electrostatic Force

If there are two unlike charges lying in the same plane in the invincity of each other. The force of attraction of the Negative Charge on the Positive Charge is calculated by the Coulomb's formula

F = k \frac{ Q_+ Q_-}{r^2}

Electrodynamic Force

If there is an Electric Force that makes stationary charge to move in straight line motion then the Electric Force is called Electromotive Force can be calculated by Ampere's Law

F_E = E Q

If there is Magnetic Force that makes moving charge to move in straight line perpendicular to the initial direction then the Magnetic Force is called Electromagnetomotive Force can be calculated by Lorentz's Law

F_E =B v Q

Electromagnetic Force

The sum of Ampere's Law and Lorentz's Law on a moving charge is called ElectroMagnetic Force and can be calculated by

F_EB = F_E + F_B = Q ( E + v B )

Matter and Electricity

All matters interact with Electricity are divided into three group

  • Conductor . All matter that allows current to flow easily through them . For example Copper (Cu) , Ferrite (Fe) , Zinc (Zn)
  • Non Conductor . All matter that does not allow current to flow through them . For example Wood , Rubber
  • Semi Conductor . All matter that allows current to flow with some ease between a Conductor and Non Conductor . For example Copper (Cu) , Ferrite (Fe) , Zinc (Zn)

Conductor and Electricity

Electron flow in a conductor.svg

When a Conductor is connected with Electric source . The Electric source will exert a Pressure to force electric charges to move in straight line . Pressure of the Electric source is called Voltage denoted as V measured in Volt (v) . The flow of electric charge in a straight line is called Current denoted as I measured in Ampere (A)

Electric Characteristics Definition Notation Formula Unit
Voltage Electric Pressure that force Electric Charge travel in a straight line V  V = \frac{W}{Q} V
Current The flow of Electric Charge in a straight line I I = \frac{Q}{t} A
Resistance The ratio of Voltage over Current R R = \frac{V}{I} Ω
Conductance The ratio of Current over Voltage G G = \frac{I}{V} S
Power Supply Product of Voltage and Current PV P = V I = (\frac{W}{Q}) (\frac{Q}{t}) = \frac{W}{t} J
Power Loss Power of Electricity lost during conversion of Electricity to Heat PR P_R = V_R I_R
P_R = I_R^2 R
P_R = \frac{V_R^2}{R}
Power Transmitted The difference of Power Supply Power Loss P P = P_V - P_R
P = V I - I^2 R
P = I ( V - IR )
Power Efficiency Power Efficiency is used to measured the efficiency of Power Transmitted over Power Supply n n = \frac{P}{P_V}
n = \frac{P Cos \Theta}{P} = Cos \Theta
n = \frac{V - IR}{I}
n = \frac{I - \frac{R}{R}}{I}

Conductor's Resistance and Heat Dissipated

Every Conductor when transmit current will release Heat's Energy into the surrounding calculated by

 P_R = V_R I_R = I^2 R = \frac{V^2}{R}

Conductor's Resistance and Temperature

Resistance of Any conductor will increase with increasing temperature

Matter Conductor Semi Conductor
Resistance R = R_0 (1 + \alpha T) R = R_0 e^(\alpha T)

Black Body Radiation

Every Conductor when conducts current will exibit Change in Temperature and release Radiant Heat Energy into the surrounding . This is called Black Body Radiation. Radiant Heat Energy of a Black Body Radiation is a wave that has dual Particle Wave Like characteristics . Sometime it behaves as a Wave sometime it behaves as a Particle

Frequency Speed Wavelength Energy
f < fo v = λ f \lambda = \frac{v}{f} E = m v2
f = fo v = c \lambda = \frac{c}{f_o} E = h fo
f > fo v = c \lambda = \frac{c}{nf_o} E = h nfo

Photo Electric Effect

Photoelectric effect.svg

There are Light when shine on matter does make matter eject Electron of matter's surface to become free electron and change the matter's Conductivity . This is called Photo Electric Effect

In Photo Electric Effect. When light is shoned on matter, matter absorbs the Heat energy of light upto its maximum capacity of absorption and then any excess energy is used to eject electrons of matter's surface

Light Energy = Heat Absorb + Energy to eject Electron
hf = hfo + ½ m v2

In order to have a free electron

hf > hfo for v > 0
f > fo

The Photo Electric Effect only take place when Light of frequency f is greater than the threshold Frequency of matter fo

Lights that have this characteristic include

  1. Sun Light
  2. Radiated Light of Black Body Radiation
  3. Electromagetic Light of Radioactive Radiation like streams of Alpha, Beta, and Gamma particles that travels at Speed of Light



ElectroMagnetic is found in current conducting coil made from a straight line conductor with several turns. When there is no current the coil does nothing . When the is current. The coil generates Magnetic Field just like Magnetic Field of Magnet. Therefore, Current Conducting Coil is known as ElectroMagnet. ElectroMagnet has two poles namely North Pole and South Pole correspond to polarity of current. Noth Pole is Positive . South Pole is Negative . ElectroMagnet has a Magnetic Field consist of Magnetic Field Lines running from North pole to South Pole

When the Coil conducts current it generates Magnetic Field calculated by

B = L I

Take Derevative of the equation above

\frac{dB}{dt} = \frac{d LI} {dt} = I \frac{dL}{dt} + L \frac{dI}{dt} = L \frac{dI}{dt} .

Change of Current generates Change in Magnetic Field this creates a Voltage on the coil that has polarties like polarities of current that generates Magnetic Field

 V_L = L \frac{dI}{dt} = \frac{dB}{dt}

ElectroMagnetic Induction

When the coil conducts current, the coil will generate Magnetic Field on the coil. This Magnetic Field in turn generates Magnetic Field on the coil's turns called Magnetic Flux denoted by Φ calculated by

Φ = B N

Take deravative of equation above

\frac{d\phi}{dt} = \frac{d NB} {dt} = B \frac{dN}{dt} + N \frac{dB}{dt} = N \frac{dB}{dt}

Change in Magnetic Field on the coil generates change in Magnetic Flux on the coil's turns which creates an Induced Voltage that has current's polarities opposite to the polarities of the current generates Magnetic Field

-ξ =  N \frac{dB}{dt} = \frac{d\phi}{dt}

Permanent ElectroMagnet

Permanent ElectroMagnet can be produced by placing a magnetic conducting object completely inside the turns of a ElectroMagnet Coil . When turn off current or when take the object out of the ElectroMagnet Coil, The Permanent ElectroMagnet still has its Magnetic Field . Therefore, the object is known as Permanent ElectroMagnet


  1. When the Coil of a straight line conductor of several turns conducts current The Coil generates Magnetic Field
  2. Change in Current produce Change in Magnetic Field and a Voltage that has polarities the same as polarities of Current that generates Magnetic Field
  3. Change in Magnetic Field in the turns of the Coil produce an Induced Voltage that has polarities opposite to the polarities of current generates Magnetic Field

ElectroMagnetic Wave

ElectroMagnetic Wave is a wave made from two waves, Electric Wave and Magnetic Wave perpendicular to each other .

When there is an Electric Force that make stationary electron into straight line motion . This Force is called an Ampere's Force calculated by

F = E Q .

Ampere's Force creates an Electric Field E

E = \frac{F}{Q}

When there is a Magnetic Force that makes moving electron to move in straight line motion perpendicular to the initial moving direction. This Force is called Lorent's Force.

F = B Q v .

Lorent's Force creates a Magnetic Field

B = \frac{F}{Q v}

Add Ampere Force and Lorent's force will give ElectroMagnetic Force that has two fields Electric and magnetic perpendicular

F = E Q + B Q v = Q (E + B v)

  1. In general, When there is moving Electrons and when there is Change in Magnetic then ElectroMagnetic Wave will exist
  2. All ElectroMagnetic Wave moves in space with a speed equal to speed of Light in the vaccum . V = C = λ f
  3. Since all ElectroMagnetic Wave moves at speed equal to speed of light therefore if one of the parameters is known the other parameter can be calculated
\lambda = \frac{C}{f}
f = \frac{C}{\lambda}


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