Voltage, Current And Resistance Exercise

claudia

12th May 2007 - 02:38 PM

Please help with the following exercise:

Given 2 resistors in series R1=10 ohms, R2= 30 ohms, determine the current flowing through the resistors and the voltage across each resistor, if the potential difference across the wire is V=12V.

This is how I solved it:

The total resistance Req= R1+R2= 40 ohms

R = V / i
i = V/R = 0.3 A

V(R1) = -R1*i = -10*0.3= -3V
V(R2) = -R2*i = -30*0.3= -9V

Is it correct? Can the voltage be negative? Please help.

Thank you.

Ron

12th May 2007 - 03:01 PM

Hi Claudia,
Well done, although your choice of signs is not right. If you draw the schematic of it, you'll see that the voltages across each resistor is positive towards the positive supply and negative toward ground, since your +12V is referenced to ground, your resistor voltages must be also.
Way to break down a problem!
Peace,
Ron

PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.