Max Voltage: 3 100ohm Resistor Circuit | Homework Solution

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The discussion focuses on calculating the maximum potential difference between points A and B in a circuit with three 100-ohm resistors, where each resistor can dissipate a maximum of 25W. Initially, the user attempted to simplify the circuit to a single 150-ohm resistor and used the formula P=V^2/R, resulting in an incorrect voltage of 61V. The correct approach involves determining the maximum current through the first resistor using P=I^2R, which yields a maximum current of 0.5A. Subsequently, applying Ohm's Law (V=IR) with the equivalent resistance gives a maximum voltage of 75V. The final answer confirms the correct maximum potential difference.
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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.
 

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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?
 
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
 
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