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resistor in series and in parallel

resistor in series and in parallel

I already tried to solve this problem but I think i'm using the wrong formula. Three 100 Ohms resistors are connected two in parallel and the other one is in series with the other two between a and b. The maximun power that can safety be delivered to any one resistor is 25.0 V. (a) What is the maximum voltage that can be applied to the terminals a and b? (b) for the voltage that determined in part (a), what is the power delivered to each resistor? What is the total power delivered? What i did first was, calculed the equivalent resistance circuit and then I calculed the potential difference, but I got something very defferent comparing with the answer. Please, would you give me a hint, thanks.
1 REPLY 1

resistor in series and in parallel

On 10/5/2003 11:08:57 AM, ernestoeca wrote:
>I already tried to solve this
>problem but I think i'm using
>the wrong formula. Three 100
>Ohms resistors are connected
>two in parallel and the other
>one is in series with the
>other two between a and b. The
>maximun power that can safety
>be delivered to any one
>resistor is 25.0 V. (a) What
>is the maximum voltage that
>can be applied to the
>terminals a and b? (b) for the
>voltage that determined in
>part (a), what is the power
>delivered to each resistor?
>What is the total power
>delivered? What i did first
>was, calculed the equivalent
>resistance circuit and then I
>calculed the potential
>difference, but I got
>something very defferent
>comparing with the answer.
>Please, would you give me a
>hint, thanks.

I presume you meant 25 watts as the maximum power?

The single resistor is the choke point, you cannot supply more current than its power rating will allow. so I2R < 25 watts, resulting in a maximum current of 0.5 amps. Since the two parallel resistor result in 50 ohms, the total resistance between a and b is 150 ohms. With 0.5 amps, this results in 75 volts applied. Since the parallel portion has equal resistors, the current must be equally split between the two.

Can you take it from here?

TTFN,
Eden
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