The Student Room Group

anyone fancy helping me with electrical?

sort me out boys and girls
Original post by NikelbackRokay
sort me out boys and girls


What's the problem?
Yes, electrical what?
Original post by Reality Check
Yes, electrical what?


i need help with working out a circuit
Original post by Mvine001
What's the problem?


got a circuit i do not know how to work out
Original post by NikelbackRokay
got a circuit i do not know how to work out


Show this circuit
Original post by Mvine001
Show this circuit


goodluck electrical q.png
Original post by NikelbackRokay
goodluck electrical q.png


Just while Im working it out, have you tried looking at the mark scheme for this question?
Original post by Mvine001
Just while Im working it out, have you tried looking at the mark scheme for this question?


nah i don't have one
Original post by NikelbackRokay
nah i don't have one


You do realise that there are mark schemes online, right?
Original post by Mvine001
You do realise that there are mark schemes online, right?


how do i find them?
Original post by NikelbackRokay
how do i find them?


Put in whenever the paper is, followed by the type of paper.
Original post by Mvine001
Put in whenever the paper is, followed by the type of paper.


i just have this sheet it is homework see brah
Original post by NikelbackRokay
i just have this sheet it is homework see brah
So you want others to do your homework for you or are you stuck because you don't know how to do it?

This 'homework' will form part of your course assessment n'est pas? So you are in effect cheating.
(edited 7 years ago)
Original post by uberteknik
So you want others to do your homework for you or are you stuck because you don't know how to do it?


stuck
Original post by uberteknik
So you want others to do your homework for you or are you stuck because you don't know how to do it?

This 'homework' will form part of your course assessment n'est pas? So you are in effect cheating.


bassically brah bit stuck like fancy sorting a brother out?
Original post by NikelbackRokay
i just have this sheet it is homework see brah


Damn
Original post by Mvine001
Damn


any ideas?
First, condense every resistor in the network into a single resistor. This will enable you to find the total current flowing into R5 and hence the entire network.

1. Start with combining R8 and RL. Do that with the folllowing formula: R8Ltotal = (R8*RL)/(R8+RL).

2. Then you can combine R8Ltotal with R7 and R9 just by adding them together. This will leave you with R1 in series with 2 parallel resistors: R8, RL, R7 and R9 all combined into a single resistor - in parallel with R6.

3. Use the same formula as step 1 to condense these two parallel resistors into a single resistor.

4. Which leaves you with 2 resistors in series. Add them together to get the whole resistance of the circuit. Then use ohm's law to find the total current flowing into the circuit. This will also be the same as the current flowing through R5 - according to Krichoff's current law.

5. You then have the first junction the current is flowing into. Recall Kirchoff's current law and the "current divider" equation (similar looking but different to the voltage divider equation - be careful with that!) and use the total resistances seen "looking into" each branch that you previously worked out to find the currents flowing into them. Remember that the current flowing through each series connected resistor is the same.

6. Once you find the current flowing through each one, use Ohm's law to calculate the voltages across them. You can find the power dissipated by a resistor if you know the current through it or the voltage across it.
(edited 7 years ago)

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