Current & Resistance

CURRENT

What is current?

Current is types of energy. A flow of current is called current.

AC (Alternating Current)

          AC is short for alternating current. This means that the direction of current flowing in a circuit is constantly being reversed back and forth. This is done with any type of AC current/voltage source.

           The electrical current in your house is alternating current. This comes from power plants that are operated by the electric company. Those big wires you see stretching across the countryside are carrying AC current from the power plants to the loads, which are in our homes and businesses.

DC (Direct Current)

DC is short for Direct current. The battery we have been using for a current/voltage source generates direct current, which simply means the current flows in only one direction.

As long as electrons are flowing through the atoms of the circuit, work is being done. We can see that work is being done in this circuit because it lights the light bulb. The actual amount of electrons that are flowing is determined by the type and size of the battery as well as by the size and type of the light bulb. We could reverse the polarity of the battery by switching the contacts (wires), and the current would flow in the opposite direction and the bulb would

still light. 
            Either way the battery is connected to the circuit, current can only flow in one direction. Direct current (DC) can also be generated by means other than batteries. Solar cells, fuel cells, and even some types of generators can provide DC current.

Resistance

Resistor is an electrical component that reduces the electrical current. The resistor's ability to reduce current is called resistance and is measured in units of Ohms [Ω].If we make an analogy to water flow in pipes, the resistor is a thin pipe that reduces the water flow.

A resistor is a device that resists, or limits, the flow of electric charge through itself, in the same way that a narrow or partially blocked pipe resists the flow of water through friction. The power source driving the current through the circuit generates electrical energy, and the resistor converts that

electrical energy into heat energy.

Resistance is Show by “R” and Symbol is

Ohms  

1000 Ohms        =     1 Kilo Ohms

1000 Kilo Ohms   =     1 Mega Ohms

1 Mega Ohms     =    I Gega Ohms

 

Symbol of Ohms

Types of Resistance

1. Normal Resistance (4 Band, 5 Band)

a. Series Resistance

One by one continually of resistance is called series resistance. The total equivalent resistance of resistors in series R_Total is the sum of the resistance values:

R_Total = R₁+ R₂+ R₃+...

So when you add resistors in parallel, the total resistance increases.

                                           R₁                     +                      R₂

                        (2600 Ohm’s   5% +)      +      (6600 Ohm’s   5% +)

Total Value this resistance is 9200 Ohms 10% +      

b. Parallel Resistance

Two Resistances of the both sides joining is called parallel resistance. The total value find in the quarters (25%) result given. So when you add resistors in parallel, the total resistance decreases.

4 Band Color Code Resistance Table

Color	Band I	Band II	Band III	Band IV
Silver	-	-	X 0.01	10% +, -
Golden	-	-	X 0.1	5% +, -
Black	-	0	-	Not Use On Band IV
Brown	1	1	0
Red	2	2	00
Orange	3	3	000
Yellow	4	4	0000
Green	5	5	00000
Blue	6	6	000000
Valuate / Purple	7	7	0000000
Gray	8	8	00000000
White	9	9	000000000

  

   5 Band Color Code Resistance Table

Color	Band I	Band II	Band III	Band IV	Band V
Silver	-	-	-	X 0.01	10% +, -
Golden	-	-	-	X 0.1	5% +, -
Black	-	0	0	-	-
Brown	1	1	1	0	1%
Red	2	2	2	00	2%
Orange	3	3	3	000	-
Yellow	4	4	4	0000	-
Green	5	5	5	00000	0.5%
Blue	6	6	6	000000	0.10%
Valuate / Purple	7	7	7	0000000	-
Gray	8	8	8	00000000	0.05%
White	9	9	9	000000000	-
No Color	-	-	-		20%

2.Variable Resistance

            Variable Resistance is three legs & no color coding. Variable Resistance is show (VR). Leg 01 & 02 is Value input & leg 03 Value out.

Symbol:      

3.Micro Resistance or Micro Resistance Chip

0	Fuse
100	10 Ohms
101	100 Ohms
102	1000 Ohms
103	10000 Ohms
104	100000 Ohms
200	20 Ohms
201	200 Ohms
202	2000 Ohms
203	20000 Ohms
300	30 Ohms
302	3000 Ohms
303	30000 Ohms
470	47 Ohms