Electrical Calculations

Electrical calculations

Exploring formulas used to calculate total Ohms, Wattage, Voltage and Amps through any type of circuit whether it be an Series, Parallel or Series-Parallel.

Laws are used to determine the formula needed to calculate a desired outcome.

Theses laws include Ohms Law which uses  Volts (V) Amps (I) and Resistance (R)

To calculate the Resistance in a circuit, you have to follow the triangle.

For instance if I wanted to find the total resistance of a circuit with a 12v bulb with an amperage of 0.4Amps I would use the formula shown in the triangle.

R= V/I

So R (resistance) is equal to V (volts) ÷ I (amps)

R= 12v / 0.4a

R= 30 ohms

                               

So from using this equation I can determine that in a circuit has a 12v bulb with a amperage of 0.4a it will have a total resistance of 30Ω.

This triangle can be used to find either Resistance, Voltage or Amps. To find Voltage use IxR. and to find Amps use V÷R 

Another law that is used to measure electricity is the Power Law, which uses Wattage, Voltage and Amps to determine the desired outcome. Again for the power law you would use a triangle similar to the one used for Ohms Law.

This is the Power Law triangle. it is used to calculate the Watts in a circuit. it works the same way as the Ohms Law triangle. So if i wanted to calculate the total Watts using the same Voltage and Amps i used in the resistance equation

W(watts)= V(volts)x I(amps) 

W= 12v x 0.4a

W= 4.8w

From this equation i can determine that if I took my 12v bulb with its 0.4amps and wanted to find the total wattage of the bulb it would conclude that my bulb would have a total Wattage of 4.8watts. Again this triangle can be used to find either Watts; using VxI. Volts; using W÷I and Amps; using W÷V.

The last equation or formula that we have used in this section is Total Resistance in a Parallel Circuit, which is a fair bit more complicated then the other two because it involves more steps than the other two. First you have to find the resistance for each bulb first, which you do by using the Ohms Law. Once you have established the resistance in each of the bulbs you label them R1 (1st bulb), R2 (2nd bulb) and R3 (3rd bulb) and so on depending on how many bulbs you have. then you use the formula below

So if my first bulb had a resistance of 2Ω, second bulb had a resistance of 4Ω and my third bulb had a resistance of 6Ω my formula would go,  

Secondly you have to identify the highest common denominator which would be 6 in this instance. So the next working would go on to look like, 

the next step is to add the numbers on the top of the equation and then invert them with the denominator.

So now the final step is to divide the top by the bottom (6÷5.5) giving us the final answer of Resistance total equaling 1.091Ω

Through these 3 formulas I have shown how to find Resistance using Ohms Law, Watts using the Power Law and Total Resistance in a Parallel Circuit using the RT equation.

From these 3 formulas I am able to calculate any outcome that is needed to determine a desired outcome. Through our practical lessons we used these calculations many times. With a various range of numbers, including whole and decimal. with the decimal numbers you must round to the 3rd decimal place (0-4 stays the same 5-9 round to the nearest 10)

picture of a individual circuit

Electricity Circuits: Individual, Series, Parallel and Series-Parallel

What is electricity?

Electrons- negatively charged particles present in all atoms the movement of electrons creates electricity in a conductor.

Conductor- many material that will allow electrical current to the various circuit components, the most commonly used materials in automotive use is copper, brass, steel.

Insulator- material that has an extremely high resistance to current flow, material that will reject an electrical charge such as plastic, mica, fiberglass etc.

Semi conductor- materials that act as conductors or insulators depending on temperature physical or electrical conditions. Common materials are: germanium or doped silicon. (impurity)

Electrical terms

Voltage; (volts)

Practical unit of pressure; practical unit of electromotive force.

The force or pressure that is required to move the electrons in a circuit.

Ampere (amps)= unit of current (flow)

When electrons move along a conductor, this means there is now current flowing in the circuit measured in amperes (amps). The larger amount and flow of electrons the larger the current.

Ohms; This is the unit of resistance

The resistance to the flow of electrons.

Resistance is introduced into a circuit to reduce or limit current flow and voltage.

It is important to have an understanding of resistance for calculation purposes.

Wattage; practical unit of power. (work being done)

In an electrical circuit, if you multiply the voltage maintained across the circuit, by the amperes flowing through the circuit, this will equal the Watts being used to produce the output.

Conventional current flow; conventional current flows from positive to negative.

Electron flow; electrons flow in opposite direction to conventional current flow. Negative to positive.