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Circuit

How could we find the current that passes through each resistor in this circuit? The problem is that we don't have the voltage of each resistor to find the current, because the voltages of the resistors are not equal to the voltage of the source.

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  • \$\begingroup\$ Hello and welcome, this looks like a homework question, so i will just give a hint : could you find the current going through the whole circuit? maybe the voltage at the lower right corner? \$\endgroup\$ – Sclrx May 10 '19 at 9:30
  • \$\begingroup\$ I could find the current and the voltage in the lower right corner, but how would this help? \$\endgroup\$ – Positron12 May 10 '19 at 9:32
  • \$\begingroup\$ you would have the voltage across eah resistor, from which you could compute the current using Ohm's law. \$\endgroup\$ – Sclrx May 10 '19 at 9:33
  • \$\begingroup\$ If the I find the voltage in the lower right corner, I will the find the voltage of the equivalent resistor of R1,2,3 , how could it equal to the voltage of each resistor? \$\endgroup\$ – Positron12 May 10 '19 at 9:35
  • \$\begingroup\$ the voltage across the equivalent resistor of R1,2,3 is the same as the voltage across R1, R2 or R3 \$\endgroup\$ – Sclrx May 10 '19 at 9:40
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Start by labelling your circuit. You should know that in a series circuit, the current is the same at any point in the circuit.

schematic

simulate this circuit – Schematic created using CircuitLab

We know that because this is now a series circuit, the current at each arrow in the circuit is the same. To find the current in the circuit, just work out the parallel resistance of each branch and use Ohms Law.

Once you have done this, you can find out the voltage drop over each parallel branch, once again employing Ohms Law.

schematic

simulate this circuit

Once you have done this, you can simply apply Ohms Law to each resistor to find the current through it. To make sure you have done it right, just remember the total current in each parallel branch should equal the total current of the circuit.

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  • 2
    \$\begingroup\$ +1 for the good hints rather than a full solution \$\endgroup\$ – Elliot Alderson May 10 '19 at 10:45
  • \$\begingroup\$ @ElliotAlderson when it comes to homework questions, if I decide to answer them I will never give the actual answer, just give enough information for OP to solve it themselves. Always thought that is a much better way of helping rather than handing all the answers over. \$\endgroup\$ – MCG May 10 '19 at 11:12
  • \$\begingroup\$ How we we know that the voltage drop of the branch is equal to the voltage of each resistor in it? \$\endgroup\$ – Positron12 May 10 '19 at 16:30
  • \$\begingroup\$ The voltage drop over parallel resistors is always the same. If you redraw it as a series circuit like the first one in my answer, you will see that there cant be multiple voltage drops over it. \$\endgroup\$ – MCG May 11 '19 at 13:29

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