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The Relationship between Voltage, Current & Resistance in the Consumption of  Power

  1. 6.0 Volts, 4.16 Amps = 50 Watts

  2. 4.0 Volts, 5.55 Amps = 66 Watts

  3. 3.0 Volts, 6.25 Amps = 75 Watts

Mister OHM's LAW
"Here Come da Judge"

E  Electromotive Force measured in VOLTS
I  Intensity[1] measured in AMPS 
R  Resistance measured in OHMS 
P  Power measured in WATTS
 

[1] Early work used term Intensity for electricity in wire.

.

Resistor as a CONVERTOR

CURRENT to VOLTAGE  |  |  VOLTAGE to CURRENT
1)_ You have a 12 volt car battery. 

2)_ You connect  two 6 volt 25 Watt bulbs in series across the battery. 
    2a_ Bulb: 6 Volts, 25 Watts = 1.44 OHMS = 4.166 AMPS (1.44 x 4.166 = 6) 

3)_ Measure the voltage across both bulbs: you will measure 6 volts across each. 
      (R = 2.88 OHMS, I = 4.166 AMPS) 

4)_ Now place another 6 volt 25 Watt bulb in parallel with either bulb--say the 
      bulb closest to ground. (R = 2.16 OHMS, I = 5.55 AMPS) 

5)_ Again measure the voltage across both bulbs: 

6)_ The single bulb (top) will measure   8 volts.  (1.44 OHMS) 

7)_ The two bulbs (bottom) will measure   4 volts.   (0.72 OHMS) 

8)_ Of course both voltages will equal   12 volts. 
 

DISCUSSION: 
If we think of the bulbs as resistors (they are within reason), notice that there is 6 volts dropped across one bulb in the first example. 

In the second example, when the second bulb is added, more current is made to flow, and the voltage across the single bulb went from 6 volts to 8 volts. 

In both cases the single bulb (resistor) is CONVERTING the CURRENT to a VOLTAGE: The more current, the more voltage.

    Example #1: 4.166 AMPS across 1.44 OHMS = 6 Volts 

    Example #2: 5.55 AMPS across 1.44 OHMS = 8 Volts 
 

CONVERTING the VOLTAGE to a CURRENT
Notice that adding the second bulb in parallel increased the Current; conversely, taking away that bulb will decrease the current.

So changing the total resistance across the 12 Volt battery has converted a fixed VOLTAGE to a changing CURRENT.

SEE: Intuitive  Electronics Page
 
 

 


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