Max Voltage: 3 100ohm Resistor Circuit | Homework Solution

[TyErd]

Homework Statement

Three 100ohm resistors are connected as shown. The maximum power that can safely be dissipated in anyone resistor is 25W

What is the maximum potential differencethat can be applied between points A and B.

Homework Equations

Ohms Law, V=IR
P=V^2/R

The Attempt at a Solution

I simplified the circuit down until I had one single resistor of 150ohm then used P=V^2/R, so 25= V^2/150, rearranged and got V=61V however this is incorrect.

 

[Mindscrape]

That's not quite right. What you're doing is finding the potential across the equivalent resistor. The equivalent resistor doesn't have the same power rating. You should find the max current that can go through the first resistor because it will be what limits you.

P=I^2R

So now you know the max current, and you can find the voltage that goes between the equivalent resistor.

V=IR

Does that make sense to you?

 

[TyErd]

Okay the max. current that will go through X is 0.5A.The equivalent resistor is 150ohms so 150*.50 = 75V. Thankyou! the answer is right