Circuit Theory for Tinkerers

Like it or not, we need some basic Circuit Theory for tinkering in electrical and electronics gadgets.

BTW, changing a plug, replacing a wire, spay some paint does not count as tinkering in my book. When I tinker, I dig deep.

Where did I picked up the circuit theory know-how?

All Engineers took electrical classes somewhere along the academic route; We enter the classroom, went through the motion of listening to the teach/lecturer, collect all the handouts, do some tutorials and off we go to the exams… to return the knowledge in written form. Hopefully, some of these knowledge will residual in our brain. In my case, Ohms Law, power and summation of component value calculation stayed….

Lucky me, enough for tinkering and be dangerous.


Ohms Law

V = I · R

V is for voltage, V is the unitI
I is for current Ampere, A is the unit
R is for Resistance, Ω ohm us the unit.

From here, we can derive the following equations

I = V / R

R= V / I

Power

P = V · I

Where,
P for Power or Watt, W is the unit
V for Voltage across the component
I for current running through the component

Summation of Resistance

Series Connected Resistor,

R_total in series = R₁ + R₂ + R₃ + … + R_n

Where,
R_total is the resulted total Resistance of the series connected resistors
R₁, R₂….Rn are the Resistance of individual resistor

~handy tips,

When connecting same value resistor in series,

Use This --> R_total = R_individual x Pieces of resistors

Parallel connected Resistor,

R_total = ((R₁)^-1 + (R₂)^-1 + (R₃)^-1 + …. + (R_n)^-1)^-1

Where,

R_total is the resulted total Resistance of the connected resistors

R₁, R₂….Rn are the Resistance of individual resistor

~handy tips

When connecting identical value Resistor in parrallell

R_total = R₁ / pieces of resistor

How to use them?

• Ohm’s Law enable us to figure out how much voltage is across the component and how much current going through the component.

• We use this as the minimum required ratings, i.e. current, voltage and watt rating of the components. *PS* For Power rating, give it at least a double,I triple when I have the chance.

• Summation of resistor allow us to add/reduce R_total in the circuit. By changing the R_total, when use with Ohm’s Law, we can figure out how to adjust the current and voltage of the circuit and/or components. Which is an essential know-how for tinkering.