# NEED HELP ! Wheatstone bridge and DC series/parallel Please look!

NEED HELP ASAP! Wheatstone bridge and DC series/parallel !! Please look!

I have three problems I need help solving.

Problem #1:
Fine the value R1 in the figure if R2 = 30ohm, I = 0.5A and V = 10V

My try was:

Rp = R1 + R2 , 20 = R1 + 30 , R1 = -10?

** please look for attached diagram problem 1

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Problem # 2

You have a balanced wheatstone bridge at L2= 45cm, mark ( where L2 + L3 = 100cm ) and R1 = 100ohm, what is the unkown resistance Rx?

** please look at attached diagram for problem 2

Problem #3.

Calculate the current of A in the figure if R1 = 250ohms, R2 = 400ohms, R3 = 200ohms and R4 = 200ohms

** please look at problem 3 for the diagram attached.

I had I = V/R with 45V/450 Ohm which gave me 0.1 A I combined the resistors to 400, 400, 250 on the diagram.

#### Attachments

• problem1.jpg
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• problem2.jpg
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• problem3a.jpg
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Borg
Gold Member

For problem #1, the total resistance is 20 ohm (10v/.5A). However, the formula for resistors in parallel is not what you're using. Parallel resistance is computed using 1/R(total) = 1/R(1) + 1/R(2) + ... You have R(total) and R(2) so the resistance for R(1) should be easy to solve.

For problem #2, I'm not sure what to make of that problem.

Problem #3 does have a current of .1A

Are u sure regarding problem 2's diagram?
THERE'S NO L1,L2.

Yes problem 2's photo goes to the problem 2.

Seems like problem 4 about the Wheatstone bridge is referencing some other problem that is on the paper. It says "you have balance THE Wheatstone bridge", usually it would be written as "you have balanced A Wheatstone bridge".

but there's no L1 and L2 given in diagram.

The problem numbers on the paper dont match what ive posted here. But thats all that was given :( I have no idea