what method do i need to find the current flowing in R1 and R5? and can you show me how, i still have difficulty in calculating the electric current in a complicated circuit
simulate this circuit – Schematic created using CircuitLab
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1\$\begingroup\$ What methods you are allowed to use? For example, you already drew the schematic into the simulator so you can simply look up the result from the simulator. Otherwise just combine the series and parallel resistors until you have a simple enough circuit to calculate what you need. \$\endgroup\$– JustmeCommented Oct 20 at 10:48
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2\$\begingroup\$ Also this is basically asking the same thing than you asked for the previous circuit - how to calculate it. The answer how to calculate these circuits has not changed since the previous question. Maybe if you explained where you have difficulties and asked for help with those would help you solve these yourself. \$\endgroup\$– JustmeCommented Oct 20 at 10:56
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2\$\begingroup\$ Here's an approach you might find helpful: you're looking to simplify this circuit until it's easy enough to calculate what you need. In essence, you're looking for a pair of resistors you can replace with a single resistor, without affecting the circuit. Which means look for two resistors in series or two resistors in parallel. You try "black boxes": can you put a box around two resistor such that only two wires exit your box? If so, you can replace this pair with a single resistor. So you can box R7 and R9, but not R2 and R5. Repeat until simple. \$\endgroup\$– jonathanjoCommented Oct 20 at 11:13
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1\$\begingroup\$ Sometimes you have to redraw the wires in an electrically-equivalent way in order to draw the box: this is the case for R3 and R6, you have to slide their connections around in order to draw the box. \$\endgroup\$– jonathanjoCommented Oct 20 at 11:16
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2 Answers
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Again, as in the previous question, until you are familiar with these sorts of problems, start by redrawing into a more readable arrangement.
To find the current through R1, you need to know the total resistance of the other parallel-series branches. That is easy to work out, just use the resistor in parallel equation \$\frac{1}{Rp} = \frac{1}{Ra} + \frac{1}{Rb} + ...\$, and series equation \$Rs = Ra + Rb ...\$ which will allow you to relatively easily calculate the total.
To calculate R5 current, knowing the current through R1, you can calculate the current through R2 by working out the total resistance of the group of resistors which are together in series with R5 and simple subtraction will give you the R5 current.
answered Oct 20 at 11:16
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Just begin by redrawing. Start like this and combine resistors that are very obvious: -
Then remove the clutter: -
Then, immediately you can see that the 4 Ω resistor in red and the 5 Ω resistor in red can be combined into a 9 Ω resistor. This new 9 Ω resistor is clearly in parallel with the 40 Ω resistor (7.35 Ω): -
Do you need any more help to solve this?
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\$\begingroup\$ I found the answer but I'm still not sure if it's right or not can you help me I found 15 ohm and 30 ohm \$\endgroup\$ Commented Oct 20 at 13:26
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\$\begingroup\$ You didn't appear to understand the comment I made to you underneath the answer to your previous question. Let's deal with that first. But anyway, aren't you trying to find current (and not ohms) in this question @TenggaArlan \$\endgroup\$– Andy akaCommented Oct 20 at 13:58
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\$\begingroup\$ I tried to find this result first \$\endgroup\$ Commented Oct 20 at 14:43
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1\$\begingroup\$ I calculate that the current through R1 is 4.6875 amps. \$\endgroup\$– Andy akaCommented Oct 20 at 14:50
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