Basic Electrical TheoryOhms Law

This section is to provide only general , practical introduction to electrical theory . Circuit design and system specific electronics will be considered in another module. The focus of this module is Supplying the appropriate amount of power and delivering that power to the systems of the ROV

The Basic terminologyCharged particles – elements (usually

protons and electrons) that have electrical attraction or repulsion

Current – the flow of electrons from one location to another (represented with the letter “I”)

Voltage – the energy per unit charged in or repulsion of charged particles (represented with the letter “V” or “E”) (joules per coulomb)

Resistance – a friction like property within a wire or a component that generates a transfer of energy like heat and other forms of energy (represented with the letter “R”)

Voltage is the amount of “pressure” needed to “push” the current along, measured in volts (V)

Current is the “rate” at which the charged particles are moving through a substance, measured in amperes (“amps” or A)

Resistance is the electronic “friction” restricting the movement of the current: measured in ohms (Ω)

The relationship between voltage, current and resistance Since Electricity is invisible, we often use analogies to help us understand the different interactions that occur in a circuit

So what? What is a circuit?

A circuit is a configuration usually comprised of a power source, a conductor and something resistant

http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

This is the schematic

http://www.youtube.com/watch?v=3o8_EARoMtg&feature=relmfu

Kahn Academy

CU Physics simulations

Ohm’s Law

The interaction between the constituent parts of electrical power form a mathematical relationship famously defined as Ohm’s Law, the most famous law in all of electronics

V = I x R(or E = I x R)

Using Ohm’s Law

This configuration, sometimes called Ohm’s triangle is a useful way of remembering how to find one element when you know the other two

Examples: …

Let’s practice seeing how this works in our own circuits

http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

http://phet.colorado.edu/sims/ohms-law/ohms-law_en.html

What about Power and Energy?Power is directly proportionate to Voltage and

Current, in other words we have another formula

P = V x I(or P = E x I)

Again a triangle is useful to help us derive what we want to know from two things that we know

Remember that power is the Rate at which Energy is put to use or used up, therefore it makes sense that as the “pressure” or voltage increases and the “rate” of the movement of the current increases, then the rate of consumption must also increase

The WheelIf we substitute the constituent parts between

the two triangles mathematically we come up with an entire array of different formulas

This looks really complicated, but if you can simply remember the relationships represented in the triangles, memorizing this is not all that important.

It is useful however to see all of the possible mathematical possibilities between the four properties of electricity and to realize that if any two properties are known, than the other two properties can be derived