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9volts 20ma VS 9volts 500mA VS 9volts 1000mA


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Whats the difference between 9volts 20ma VS 9volts 500mA VS 9volts 1000mA?


1.) Yes the "flow rate"


If a power supply is at 9 volts 20mA why can't the power supply draw more current? whats making it have a limit? why can't it power up a circuit that is 500mA? (it has enough water pressure since its at 9volts)


Water analogy:


Voltage is the water pressure

Current is the FLow rate


Whats the difference between 9volts 20ma VS 9volts 500mA VS 9volts 1000mA?


Don't over look this the 9volts stays the same , so the water pressure is FIXED.


The question is how can you have the same water pressure level/limit at 9volts but have a different flow rate(current)??


So what i'm saying is 9volts(water pressure) at 20mA(flow rate)

is different than 9volts(water pressure) at 500mA(flow rate) but how and why? When the voltage is the same?


Its not just about the "FLOW RATE" because it won't power up a circuit is its not at that Flow rate. Why won't it turn on the circuit cause of the FLow rate? current= flow rate time


If a power supply is at 9volts(water pressure) at 20mA it can't power up a 500mA delay pedal why is that? its still at 9volts(water pressure) that means there is alot of water in the tank, so where is the unused water doing in the 9volts water tank?


How can 9volts (water pressure) can have 1000mA's but another 9Volts (water pressure) only be 20mA?


9volts is the level of the water in the tank so how can the flow rate be different? where is the "unused water" going or doing when its sits in the tank?



The water tank is at 9volts

Hook a water hose up to the tank, its going to have water flow



Yes i know the answers is the power supply lOAD resistor that converts voltage to current on the output, but its interesting how the voltage stays fixed but the current FLOW rate changes

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it's easy.

The current is simply a refection of the load.

The voltage is merely a reflection of the potential difference between 2 states.


As an analogy. Take a rock up the empire state building. The voltage or in this case the potential of the rock is simply a function of the earth's gravity, it's height and the mass of the rock.


Now take that rock and drop it. It falls.

Now take the same rock and let it fall down a the stairs. It falls much more slowly..

Yet in both cases the potential (or the voltage difference) is the same.


The 9 Voltage is a static state. All that matters is what it is at the beginning and what it is at the end. The current is dependent on the route the electron takes.

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It's called internal resistance. If you try to draw more than the rated current, the internal resistance causes the output voltage to ***drop***. Usually resistance goes up as a result of heating up, and maybe the supply melts internally. All supplies including batteries have internal resistance. A high current supply has less than a low current supply.

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To keep it simple, if you have a 9V pedal, you can power it with a 9V adapter as long as you make sure of the following:


1. The adapter has to have the correct polarity at the plug, and the correct plug type for the pedal you want to use it with.


2. The adapter needs to output the correct current - AC or DC. Most pedals need DC, but not all do. Make sure you get that right.


3. The amperes rating needs to be at least the amount required by the pedal. If you have a pedal that requires 200mA, you can safely power it with a adapter that provides 300mA. You will not be able to power it properly with an adapter that is rated at 50mA.

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