Electrical Circuit Calculations

[Mark Rice]

Homework Statement

Calculate the individual currents in I2 and I3 (See diagram). I basically need to know how I calculate the current at any point in that circuit and that would help me.

Homework Equations

V=IR Rseries=R1+R2... 1/Rparallel=1/R1+1/R2

The Attempt at a Solution

I honestly have no idea how to calculate this, I think the current in I3 is 2A but really amn't sure. I know it's a simply ohms law question and I know the current splits between the resitors in parallel and it's inversely to do with the total resistance, but the fact there is so much going on in the circuit isn't helping me at all. Can anyone point me in the right direction? (I calculated the total resistance to be 24 ohms so the I drawn from supply would be 2A not even sure this is correct!)

 

[Mark Rice]

Bottom resistor which is cut off is 4 ohms.

 

[gneill]

Your current from the supply, ##I_1##, is correct. Use that to pencil in the voltage drops V₁ and V₃. That should lead you to the potential difference across R2+R3. That in turn allows you to calculate the portion of that 2 A that is diverted through R2+R3. Continue in that way, applying Ohm's law and Kirchhoff's laws to incrementally determine currents and voltages.

 

[Mark Rice]

Your current from the supply, ##I_1##, is correct. Use that to pencil in the voltage drops V₁ and V₃. That should lead you to the potential difference across R2+R3. That in turn allows you to calculate the portion of that 2 A that is diverted through R2+R3. Continue in that way, applying Ohm's law and Kirchhoff's laws to incrementally determine currents and voltages.

Thanks! Just had a "light switching on moment" and it all makes sense now! Cheers :)

 

[HalfLostAndSearching]

To calculate the individual currents in I2 and I3, you will need to use a combination of Ohm's law and the equations for series and parallel resistors.

First, calculate the total resistance of the circuit by adding the resistances of R1, R2, and R3 in series. This will give you a total resistance of 24 ohms, as you correctly calculated.

Next, use Ohm's law (V=IR) to calculate the total current in the circuit. Since the voltage is given as 24V, and the total resistance is 24 ohms, the total current would be 24V/24ohms = 1A.

Now, to calculate the individual currents in I2 and I3, you will need to use the equations for parallel resistors. Remember that in a parallel circuit, the voltage is the same across all branches, but the currents split based on the individual resistance values.

For I2, since it is in parallel with R1, you can use the equation 1/Rparallel = 1/R1 + 1/R2. Plug in the values for R1 (8 ohms) and R2 (12 ohms) to get 1/Rparallel = 1/8ohms + 1/12ohms = 5/24ohms. Take the reciprocal of both sides to get Rparallel = 24ohms/5 = 4.8 ohms.

Now, you can use Ohm's law again to calculate the current in I2. Since the voltage is still 24V and the resistance is 4.8 ohms, the current in I2 would be 24V/4.8ohms = 5A.

Similarly, for I3, you can use the equation 1/Rparallel = 1/R2 + 1/R3. Plug in the values for R2 (12 ohms) and R3 (6 ohms) to get 1/Rparallel = 1/12ohms + 1/6ohms = 3/12ohms. Take the reciprocal of both sides to get Rparallel = 12ohms/3 = 4 ohms.

Again, use Ohm's law to calculate the current in I3. Since the voltage is still 24V and the resistance is 4 ohms, the current in I3 would be 24V/4ohms