# Circut problem

Please see circut and question at http://www.flickr.com/photos/[email protected]/3421275866/sizes/o/ [Broken]

Are these calculations correct???

(a)total resistance= 6.25
25/6.25= I total = 4
v=ir 4x6=20v

(b)v=ir so 20/10= 2amps
power=vi so 2x25=50watts???

Thanks

Last edited by a moderator:

LowlyPion
Homework Helper
Please see circut and question at http://www.flickr.com/photos/[email protected]/3421275866/sizes/o/ [Broken]

Are these calculations correct???

(a)total resistance= 6.25
25/6.25= I total = 4
v=ir 4x6=20v

(b)v=ir so 20/10= 2amps
power=vi so 2x25=50watts???

Thanks
Your total I is correct. But the Vab is found either by 4*Req = 4*6 = 24 or by noting that 4*1/4 is 1v and across the terminal Vab = 25 - 1 = 24. Either way works.

In b) unfortunately you have not grasped that you have a current divider with the || network and that the current through each leg is determined by Vab which is 24, divided by the resistance through that leg. You have 15Ω through the leg with the 10Ω resistor. Hence the current through the resistor is going to be 24/15.

Once you have the current through the leg, then you can use your I2R to determine power.

Last edited by a moderator: