Do we need resistor on each components?

Thread Starter

Hhenryl

Joined Sep 12, 2016
2
hi there, currently I'm a student, I want to know is it necessary to put a resistor on every components circuit?
why yes? and why not?
 

falade47

Joined Jan 24, 2017
176
hi there, currently I'm a student, I want to know is it necessary to put a resistor on every components circuit?
why yes? and why not?
As the name implies...resistor limits the flow of current...all components have specific voltage that can run them..feeding a component power more than it can take means damaging it..for instance using a 12v battery to power a 3v led..that is called #raping..so with the help of a 7805 regulator and a 1kohm resistor it woud work fine happily..remember resistance =voltage/current..
 

mtonge

Joined Apr 19, 2016
93
My high school electronics instructor drilled it into us that resistors do not resist voltage, they resist current. All circuit components have some internal resistance, but perhaps not enough to limit the maximum allowable current for the applied voltage. For example, common LEDs have a maximum allowed current of 20 milliamps and a forward voltage drop of approximately 2 volts. With a 5 volt power supply, I will need to drop the remaining 3 volts across a resistor while limiting the current to 20 milliamps. If I put a 220 ohm resistor in series with the LED, I have limited the current to about 14 milliamps (LED is bright). A 100 ohm resistor (at 5V) will over amp an LED (30ma) though may be OK for a flashing indicator. What are you currently working on?
 

mcgyvr

Joined Oct 15, 2009
5,394
hi there, currently I'm a student, I want to know is it necessary to put a resistor on every components circuit?
why yes? and why not?
The answer is No..
If a resistor is not needed for that circuit then... You don't put a resistor... Plain and simple..
 

#12

Joined Nov 30, 2010
18,223
There are plenty of times where you don't need a resistor.
For instance, a 2N4416 j-fet will allow 5 ma to 15 ma of current with its gate connected to its source. No resistor in the gate circuit, no resistor in the drain circuit, and you have a constant current source (or sink) with one part.
This generalization is way too broad. Not a good shortcut. Not a good rule. Abandon this idea.
 
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