# voltage and current sources

Discussion in 'General Electronics Discussion' started by blackcoffee, Feb 1, 2011.

1. ### blackcoffee

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0
Feb 1, 2011
hi. a voltage source provides a constant voltage irrespective of the load connected across it. and a current source provides a constant current irrespective of the load connected across it.

could i still say they obey ohm's law? i mean, how is that despite the fact that i connect different loads, the voltage or current still remains constant? why don't they change?

2. ### rob_croxford

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Aug 3, 2010
Of course it abides by Ohms law it is one of the fundamentals after all!! The voltage or current seen at the source may not change but it will when faced with a component. For instance lets take a voltage source of 10V through a resistor of value 10ohms. The source will supply a constant voltage of 10V however there will be a drop in voltage accross the resistor. This is where ohms law can be used for calulation. Firstly by calculating the current you can calculate the voltage drop seen accross the component.

3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,480
2,827
Jan 21, 2010
Remember that there is no such thing as a perfect voltage or current source.

A perfect voltage source can supply infinite current and has a zero impedance.

A perfect current source can supply infinite voltage and has an infinite impedance.

Spot the 0's and 1/0's and that's where perfection is always limited.