October 24, 2005
what is current and voltage in circuits?
confused student asked:
i get very confused when someone tells me the microcontroller gives out a voltage not a current , what is the difference between voltage and current in a circuit ?? especially how do you know which component operates on voltage or electricity , also what does this mean??
Sign Language For Babies And Beyond
i get very confused when someone tells me the microcontroller gives out a voltage not a current , what is the difference between voltage and current in a circuit ?? especially how do you know which component operates on voltage or electricity , also what does this mean??
Sign Language For Babies And Beyond
Written by: John
Filed Under: Microcontrollers
Tags: Circuits, Electricity, Microcontroller
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james rich
October 25, 2005 at 10:19 pm
voltage is a unit of measure volts regular on homes is 110 ac or 220 ac
and curren is voltage / resistence
most of the home equipment use 110 ac and the plug is that you normally can see on tv’s or radios for 220 and up is special plugs and all the equipments has a plate and you can see the voltage for that unit
charcinders
October 26, 2005 at 12:00 pm
The easiest way to think of it is to use the analogy of water in pipes. Voltage equates to water pressure and current equates to flow rate. Electrical resistance equates to resistance to water flow (or thinness of pipe).
Whether you talk in terms of voltage or current depends on the component and what you are interested in. A microcontroller for instance signals a logic 0 or logic 1 on its output pins by putting out a low or high voltage, Because it is a voltage signal the current is usually irrelevent, unless you want to drive a low-resistance load with the output pin. If you had a LED that requires 10mA to light it, you would need to know that your microcontroller output pin can supply 10mA so that it can drive the LED.
Paul F
October 27, 2005 at 8:13 am
A voltage source, like a power supply, outputs a given voltage and is capable of delivering a given current. It supplies power.
When connecting a load (i.e. a resistor), the power supply will deliver a current to the load. Example; if the PS voltage is 10 Volts, and the resistor is 100 Ohms, a current of 10/100=0.1 Amps (Current=Voltage/Resistance) will flow through the resistor.
The power dissipated by the resistor will be 10 Volts*0.1 Amps= 1 Watt. Power=Voltage times Current.
The micro-controller you mentioned is a voltage source and is capable to deliver a small current to the load, so the load will have to have a large resistance.
Bob D
October 29, 2005 at 6:44 am
If you take, say, a 9 volt battery and hook a good volt meter across the battery terminals, you will measure 9 volts. That is just the voltage potential of the battery, no actual current is flowing.
Now, if you hook a 18 ohm resistor across (parallel with) the battery, the volt meter will still read 9 volts but the battery is now supply current to the 18 ohm resistor, I = E / R, 9 volts / 18 ohms = 0.5 Amps.
Thank of the 0.5 Amps of current as the amount of “work” the 9 volt battery is doing on the 18 ohm resistor.
A voltage source never delivers any current unless the voltage source is connected to (looking into) an actual load. A current source is a little more complicated. A battery is a voltage “source” if it is connected across (parallel) the load. A battery is a current “source” if it is connected in line (series) with the load.
Voltage Source
Current Source
What is the difference and what does it mean? Well, it’s kind of hard to explain but it has to do with how voltages and currents are used to create “power” such as heat or maybe radio carry waves. Power = I x E, Power = Current x Voltage. Also = I^2 x R If you want to increase your power output but want E to remain constant, you would use a current source to increase your current through the load, R. If, on the other hands, current in the circuit was constant, you would increase the size of E (the Voltage source) in order to increase power output.
Does that kind of make any sense?
Power electronics