Calculating Current and Voltage in Series and Parallel Circuits

[jsalapide]

1.Find the equivalent resistance seen by the source and use the result to find i, i sub1, and v.

the equivalent resistance i got is 8 ohms
my value for i is 6A
and my value for i sub1 is 1A
my v is 40V,,

are my answers correct?? help.. I am quite unsure of these..

 

[LowlyPion]

Not quite. Your equivalent resistance is correct. That's the good news.

But the I_i through the smaller of the parallel resistors would be bigger than the I₂ of the larger resistor wouldn't it? I think you have the currents reversed. Namely that the current divides 5:1 alright, but the 5 goes through the smaller R, and the 1 through the larger.

Also, you know that the current is 6A from the power source. The voltage drop across the first R then will be 3*6 = 18V. That means that the voltage on the other side of the 3Ω is going to be 18V less than 48 or 30V, not 40 as you have written.

 

[jsalapide]

does that mean that the value of v is 30V?
if that's the case, what would be the voltage on the resistor that has 6 ohms?

Or should the voltage of the 6 ohms and 30 ohms resistor be the same? Because its already parallel.. am i right?

 

[ideasrule]

"Or should the voltage of the 6 ohms and 30 ohms resistor be the same? Because its already parallel.. am i right?"

Absolutely. Resistors in parallel have the same voltage across them.

 

[LowlyPion]

Or should the voltage of the 6 ohms and 30 ohms resistor be the same? Because its already parallel.. am i right?

They are in parallel to the same nodes. And that node is at 30V. So ... yes the same voltage across both.

30V/6 = 5A and 30A/30 = 1 ... 5 + 1 = 6

The current's right. The voltages are right.

Alessandro Volta, Gustav Kirchhoff and Georg Ohm are all happy, even if all dead.