4.) Resistors & Ohm's Law

[FOOKz™]

Legend:
   Purple -  resistance
   Yellow -  power/Wattage
   Green -  current/Amps
   Red -  Voltage



Ohm's Law is the fundamental formula for electronics' Voltage, current, resistance, and power.

Voltage is expressed as the letter V or E
   Voltage's technical name is called electromotive force or EMF

current or Amps is expressed as the letter I or A

resistance is expresses as the letter R
   resistance's technical name is opposition to electron flow.

power or Watts is expressed as the letter W or P

current is normally called Amps.
power is also normally called Watts.


All of The Ohm's Law Formulas are:


To Find current--
   Voltage Divided By resistance: I =  V / R
   power Divided By Voltage: I=  P / V
   Square Root of power Divided By resistance: I = √(P / R)

Electric current is the flow of an electric charge.


To Find VOLTAGE --
   power Divided By current: V = P / I
   resistance times current: V = R * I
   Square Root of power times resistance: V = √(P * R)



To Find POWER --
   Voltage Times current: P = V * I
   Voltage Squared Divided by resistance: P =    V² / R
   resistance Times current Squared: P = R *    I²



To Find RESISTANCE --
   Voltage Divided By current: R = V /  I
   Voltage Squared Divided by power:R = V² /    P
   power Divided by current Squared: R = P /    I²


BEGINNER'S PRACTICE:

	#1 GIVEN: Resistance = 274 Ohms Voltage = 14.5 Volts Find my CURRENT and POWER.
	#2 GIVEN: Resistance = 8560 Ohms (8.560K Ohms) Voltage = 5 Volts Find my CURRENT and POWER.
	#3 GIVEN: Resistance = 1.2K Ohms (or 1200 Ohms) Voltage = 12 Volts Find my CURRENT and POWER.
	#4 GIVEN: Resistance = 453 Ohms Current = 3 Amps Find my VOLTAGE.
	#5 GIVEN: Resistance = 6.7K Ohms Power = 37 Watts Find my CURRENT and VOLTAGE.
	#6 GIVEN: Power = 1.3 Watts Current = 400mA (or 0.4 Amps) Find my VOLTAGE.

BEGINNER'S PRACTICE ANSWERS:

1.] [spoiler]

(Voltage=14.5 VOLTS) (Resistance=274 OHMS) (Current=) (Power=)[/spoiler]

2.] [spoiler]

(Voltage=) (Resistance=8560 OHMS) (Current=) (Power=)[/spoiler]

3.] [spoiler]

(Voltage=12 Volts) (Resistance=1200 Ohms) (Current=) (Power=)[/spoiler]

4.] [spoiler]

(Voltage=) (Resistance=453 Ohms) (Current=3 Amps)[/spoiler]

5.] [spoiler]

(Voltage=) (Resistance=6700 Ohms) (Current=) (Power=37 Watts)[/spoiler]

6.] [spoiler]

(Voltage=) (Current=0.4 Amps) (Power=1.3 Watts)[/spoiler]










NOVICE PRACTICE:


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NOVICE ANSWERS:

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3.] [spoiler]asdf[/spoiler]
4.] [spoiler]asdfa[/spoiler]
5.] [spoiler]asdf[/spoiler]
6.] [spoiler]asdf[/spoiler]
















ADVANCED PRACTICE:

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ADVANCED ANSWERS:

1.] [spoiler]asdf[/spoiler]
2.] [spoiler]asdf[/spoiler]
3.] [spoiler]asdf[/spoiler]
4.] [spoiler]asfd[/spoiler]
5.] [spoiler]asdf[/spoiler]
6.] [spoiler]asdf[/spoiler]

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[RDC]

They have several uses.

Pick n Place machines can't install jumper wires, so if the PCB design needed any, a 0ohm SMT Resistor does the same thing, though not over as large of a distance. The N64 controller board is an example where they are used as jumper wires since that PCB is single sided, and it also has thru hole jumpers as well. If you look around in enough different PCBs, even a lot newer than the N64, you'll see them sooner or later.

They can be useful for having a PCB with multiple configurations, used like jumpers when building it to set it up for this or that.

They can be pulled to easily break a connection to do troubleshooting instead of having to hack the board up.

Could be used as a last ditch fuse, though not recommended.

Another reason is to join different ground sources together, so you don't get all kinds of noise or have a way to isolate them for testing. In robot designing, one would be used there to join the Digital ground to the power ground, so you minimize that noise from the motors getting into the control circuitry, and can test for things as well.