How Do You Calculate Current and Voltage in Series and Parallel Circuits?

In summary, the circuit contains parallel resistors with a combined resistance of 4.54 kOhms. The total resistance is 15.04 kOhms and the total current is 1.0971 x 10-3 A. The potentials at points A, B, and C are 16.5, 11.5, and 0 volts, respectively. The current through the 10.5 kOhm resistor is 1.0971 x 10-3 A, while the current through the parallel pair is also 1.0971 x 10-3 A. The voltage across the 10.5 kOhm resistor is 11.5V and the current is 0.
  • #1
tony873004
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In the circuit shown, find the current in each resistor and the values of the potential at points A, B, and C.
26_43.GIF


First I computed the combined resistance of the parallel resistors and got 4.54 kOhms. Then I added this to 10.5 to get 15.04 kOhms total resistance.

So from Ohm's law, the total current is I=V/R = 16.5 / 15040 = 1.0971 x 10-3 A.

I get potentials at A, B, and C of 16.5, 11.5, and 0 volts.

I think this is correct so far.

To find the current through each resistor:

For the 10.5 kOhm resistor, since it is in series, it makes sense to me that the current through this resistor must be equal to the total current: 1.0971 x 10-3 A. And that the current running through the parallel pair must also be 1.0971 x 10-3 A. But the voltage across this resistor is 16.5-11.5, or 5v. Using Ohm's law, I=V/R, I get 5/10500 = 0.000476 A

Which way is correct?
Thanks
 
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  • #2
The currents through the two resistors in parrallel will be different. you have to work out the current from the voltage drop across each of the resistance's, which is 5V for both according to your calculations, and the resistance. This will give you the current in each element. It will add up to the total loop current.

Your using the wrong voltage. 5V isn't dropped across the 10.5kOhm, 11.5V is. As it's 11.5V at one side and 0V at the other.
 
  • #3
Mike Cookson said:
...Your using the wrong voltage. 5V isn't dropped across the 10.5kOhm, 11.5V is. As it's 11.5V at one side and 0V at the other.

Thanks! That's where I messed up. 11.5/10.5E3 = the same as the total loop current.

Thanks for the explanation.
 

Related to How Do You Calculate Current and Voltage in Series and Parallel Circuits?

1. What is the difference between series and parallel resistors?

In a series circuit, resistors are connected one after the other, creating a single path for current to flow. In a parallel circuit, resistors are connected side by side, creating multiple paths for current to flow. This results in different overall resistance and current flow.

2. How do I calculate the total resistance in a series circuit?

In a series circuit, the total resistance is equal to the sum of all individual resistances. So, to calculate the total resistance, simply add up the values of all the resistors in the circuit.

3. How do I calculate the total resistance in a parallel circuit?

In a parallel circuit, the total resistance is less than the smallest individual resistance. To calculate the total resistance, use the formula: 1/R(total) = 1/R1 + 1/R2 + 1/R3 + ... + 1/Rn, where R1, R2, R3, etc. are the values of each resistor.

4. What happens to the total resistance in a series circuit when more resistors are added?

In a series circuit, adding more resistors increases the total resistance. This is because the current has to flow through each resistor, causing more resistance.

5. What happens to the total resistance in a parallel circuit when more resistors are added?

In a parallel circuit, adding more resistors decreases the total resistance. This is because the current has more paths to flow through, reducing the overall resistance.

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