PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Basic Electricity Circuits Ohms Law and formulas

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS (I or A) Current ‑ Flow of electrons through a conductor as a result of pressure applied ‑ I ‑ Intensity -A- Amperage (E or V) Voltage ‑ Force or electrical pressure that moves electrons ‑ E ‑ Electromotive force -V- Voltage (R) Resistance ‑ Opposition to current flow or electrical restriction

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit ‑ Single path same current flows through each component

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Laws

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {E = volts Most auto techs use the letter V} The sum of the individual voltage drops in a series circuit equals the applied voltage.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Two Definitions you will need to know when dealing with voltage. Open Circuit Voltage or OCV Voltage when no load is applied to the car. Applied Voltage Voltage when a load is applied to the car. (Headlights are on)

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {I = current or amps Most auto techs use the letter A} In a series circuit, the current flowing in the circuit is the same at any point. Terms to know Note I t = current Total

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {R = resistance} Individual resistance in a series circuit add up to the total circuit resistance. R t = R 1 + R 2 + R 3 Terms to know R t = Resistance Total

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel Circuit ‑ More then one path, voltage is the same at each branch of the circuit.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel Circuit Laws

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {E = volts} In a parallel circuit, the voltage is the same across each branch.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {I = current or amps} The total current in a parallel circuit is equal to the sum of the individual branch currents.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS {R = resistance} The total resistance in a parallel circuit is always less than the smallest resistive branch

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series parallel, combination of both circuits

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS It takes one volt to push one amp though one ohm of resistance

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Ohm’s Law to find E = I x R I = E ÷ R R = E ÷ I E I x R Amperes = I - Intensity Volts = E - Electromotive force Ohms = R - Resistance

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Ohm’s Law For Auto techs’ to find V = A x R A = V ÷ R R = V ÷ A V A x R Amperes = A - Amperage Volts = V - Voltage Ohms = R - Resistance

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Resistance Total R t = R 1 + R 2 + R 3

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R1 = 1002 R2 = 99 R3 = 984 Rt = 2085

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Current Total E t I t = R t I t = Amps Total

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R1= 2 Ω R2= 2 Ω R3= 2 Ω R t = 6 Ω V or E = 12 E t 12 2 I t = R t 6 R1 = 2 Ω R2 = 2 Ω R3 = 2 Ω Series Circuit Current Total Example 12V

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Voltage drop across each resistor E= I t X R 1 E= I t X R 2 E= I t X R 3

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R1= 2 Ω R2= 2 Ω R3= 2 Ω R t = 6 Ω R1 = 2 Ω R2 = 2 Ω R3 = 2 Ω Series Circuit Current Total Example Finding Volts I t X R 1 = E 2 X 2 = 4 I t X R 2 = E 2 X 2 = 4 I t X R 3 = E 2 X 2 = = 12 Volts I t = 2

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R1= 2 Ω R2= 4 Ω R3= 6 Ω R t = 12 Ω R1 = 2 Ω R2 = 4 Ω R3 = 6 Ω Series Circuit Current Total Example 2 I t X R 1 = E 1 X 2 = 2 I t X R 2 = E 1 X 4 = 4 I t X R 3 = E 1 X 6 = = 12 Volts I t = 1 12V E t 12 1 I t = R t 12

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Voltage drop across each resistor To find Voltage drop across each resistor you first must find I t. Take Voltage (12) and divide by R t Which is 10 the answer is 1.2 = I t Then take I t X R 1 = Voltage drop of R X 2 = 2.4 I t X R 2 = Voltage drop of R X 4 = 4.8 I t X R 3 = Voltage drop of R X 4 = = 12 R1 = 2 Ω R2 = 4 Ω R3 = 4 Ω 12V

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Series Circuit Voltage drop across each resistor If there are only 2 resistor’s and they are the same size just take voltage divide by 2 and you have voltage drop V ÷ 2 Any number of Resistor’s all the same size. V ÷ # of Resistor’s = Voltage Drop

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R 1 x R 2 Rt = R 1 + R 2 Parallel circuit Resistance Total if only 2 Resistors

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R 1 x R 2 R t = R 1 + R 2 R2 = 4 Ω R1 = 2 Ω 2 X 4 = 8 R t 1.33 = = 6 Note R t is less the Smallest resistor

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel circuit Resistance Total if 3 or more Resistors 1 _ R 1 + R 2 + R 3 + R 4

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS R t if 3 or more Resistors 1 _ R 1 + R 2 + R 3 R1 = 2 Ω R2 = 4 Ω R3 = 6 Ω 1 _ _.917 R t = 1.09 Ω ==

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel circuit Resistance Total if Resistors are all the same value Value of one Resistance R t = Number of Resistances

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel circuit Current flow E t I t = R t

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel circuit Current flow E t I t = R t 12V 6A = 2 Ω

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS Parallel circuit Current flow of a branch I branch a = E R 1 I branch b = E R 2

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The Power Triangle or Joules Law For calculating using Power (W) Current (A) and voltage (V) Used in the same way as the Ohms Law triangle we can use the same method to see the relationship between power (W), current (A) and Voltage (V).

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The Power Triangle Power = Current x Voltage P = A x V Current = Power over Voltage A = P ÷ V Voltage = Power over Current V = P ÷ A P A x V

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The Power Triangle P = Watts Horsepower (hp) Some electrical devices such as electric motors have a power (W) rating in horsepower to which a conversion of 1hp=746W would be required for calculations.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The history of the terminology Each of the units of measurement are named after famous experimenters in electricity and energy Voltage, Volts (V) named after the Italian Alessandro Volta known especially for the development of the first electric cell or modern translation "the battery" in Amps (A) named after the Frenchman Andre M.Ampere one of the main discoverers of electromagnetism. Ohms (Ω) named after the German Georg Simon Ohm a physicist who began his research with the recently invented electrochemical cell (invented by the Italian Alessandro Volta). Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential difference (Voltage) applied across a conductor and the resultant electric current now known as Ohms Law.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The history of the terminology Each of the units of measurement are named after famous experimenters in electricity and energy Watts (W) named after the Scotish inventer and mechanical engineer James Watts who's name was adopted as a measurement by the second congress of the British association for the advancement of science in Joule (J) named after the English physicist James Prescott Joule in recognition of his work on heat and it's relationship to mechanical work or energy.

PHSAUTOMOTIVESALSPHSAUTOMOTIVESALS The end Thanks to the toolboxshop.com for the info on power