# voltage in parrallel circuits

Joined Mar 4, 2006
1
How do you find the voltage in a parrallel circuit if it is not given?

Ex. if you had 3 resistor 1ohm,2ohm, and 3ohms split into 3 branches with a 500mA current

#### hgmjr

Joined Jan 28, 2005
9,029
Originally posted by VADER332@Mar 4 2006, 05:02 PM
How do you find the voltage in a parrallel circuit if it is not given?

Ex. if you had 3 resistor 1ohm,2ohm, and 3ohms split into 3 branches with a 500mA current
[post=14667]Quoted post[/post]​
Without a diagram to go by it is tough to figure out what you have described.

hgmjr

#### beenthere

Joined Apr 20, 2004
15,819
Hi,

You have not given enough data to us. With the 3 resistors in parallel, the equivalent resistance will be less than the smallest discreet resistor, so Rt will be under 1 ohm. With no additional resistance given, we can only suggest a very low source voltage that will source the 500 mills current.

#### Grant

Joined Mar 5, 2006
17
Originally posted by VADER332@Mar 5 2006, 09:02 AM
How do you find the voltage in a parrallel circuit if it is not given?

Ex. if you had 3 resistor 1ohm,2ohm, and 3ohms split into 3 branches with a 500mA current
[post=14667]Quoted post[/post]​
The three resistances in parallel will give a total resistance of 0.55 Ohms-(using resistances in parallel equation). If you have a total current of 500mA then simply using Ohm's Law we have E=IxR
(500mA is 0.5 Amps)
E= 0.5x0.55
E= 0.275 Volts
Hope this explains it to you.
Cheers,
Grant

#### alva

Joined Dec 14, 2005
12
Originally posted by VADER332@Mar 4 2006, 05:02 PM
How do you find the voltage in a parrallel circuit if it is not given?

Ex. if you had 3 resistor 1ohm,2ohm, and 3ohms split into 3 branches with a 500mA current
[post=14667]Quoted post[/post]​

If the current is 500 mA before splitting up between the 3 branches, then you need to solve R then you can get the voltage. E =IR.

For parallel resistors you can simply add the ohm value reciprocals and then use the reciprocal of the total. e.g. 1/1 + 1/2 + 1/3 = 6/6 + 3/6 + 2/6 = 11/6 = 6/11 =.545 or .55 ohms; then solve for E : E= .55 ohm x .5 A = .275V
And in a parallel circuit the total resistance will always be less than the lowest ohm resistor, in this case 1 ohm.