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can anybody explain this to me.. why theres no current flow across R1 and R2?
Hi,.
Do you know how to calculate the sum/result of resistors in parallel.??
The short circuit is considered as zero ohms.
E,
You can find parallel resistance by the formula,
1/(1/R1 + 1/R2 + 1/R3)
Use the resistances given for R1 and R2 in the formula, and use 0 ohms for R3. Notice something? You're trying to divide 1/0. That effectively gives you infinity ohms. What's happening is that all the current is going through the short (since it's the path of least resistance--in theory no resistance at all--so the current isn't going to go through elements with a higher resistance. Make sense?
Matt
hi,You can find parallel resistance by the formula,
1/(1/R1 + 1/R2 + 1/R3)
Use the resistances given for R1 and R2 in the formula, and use 0 ohms for R3. Notice something? You're trying to divide 1/0. That effectively gives you infinity ohms. What's happening is that all the current is going through the short (since it's the path of least resistance--in theory no resistance at all--so the current isn't going to go through elements with a higher resistance. Make sense?
Matt
hi,
I thought we agreed that we would not give direct answers to Homework questions, only hints or clues.??
E.
i opologies for my rude behaviour... please forgive me...
and for the next question .. is there a voltage drop across those resistor?
hi,
I thought we agreed that we would not give direct answers to Homework questions, only hints or clues.??
E.
i am guessing theres 0v voltge drop across both of em' ..am i right?
hi,
No problem.
If you had calculated the total resistance including the short circuit of Zero Ohms, then used Ohms Law it would have shown you that you have Zero volts across the resistor network, hence no current.
A point to study would be the effect of the voltage driving sources internal output resistance.
All voltage sources have some internal resistance, even though it maybe very low, this would limit the short circuit current.
E.
thank you sir...and i am guessing that theres an infinite resistance in a voltmeter right? because if theres no resistance in the voltmeter then i assume it will be like a short circuit .
You can find parallel resistance by the formula,
1/(1/R1 + 1/R2 + 1/R3)
Use the resistances given for R1 and R2 in the formula, and use 0 ohms for R3. Notice something? You're trying to divide 1/0. That effectively gives you infinity ohms. What's happening is that all the current is going through the short (since it's the path of least resistance--in theory no resistance at all--so the current isn't going to go through elements with a higher resistance. Make sense?
Matt
07kim,
consider the below example.
The Ri is the internal resistance of the battery. You have two resistors in parallel and the wire with a very small resistance shorting out the two parallel resistors. If you hooked up your meter to measure the voltage acrossed the resistor you would read a very small value. If you hooked up an ammeter to measure the current through the resistor, you would read a very small value. If you decreased the value of the internal resistance and the resistance of the wire shorting across the two parallel resistors, well, you can configure an excel spreadsheet to calculate them out as easily as I can so you can instantly see how the resistances affect the circuit.
A minor reminder that voltage is measured acrossed a resistor and current flows through a resistor.