# How to balance the bridge?

Discussion in 'Electronics Homework Help' started by charmcaster.engg, Jan 17, 2015.

1. ### charmcaster.engg

79
1
Mar 20, 2014

In the given circuit, what is RUNK equal to if RV must be adjusted to 1,232 in order to balance the bridge?

2. ### KrisBlueNZSadly passed away in 2015

8,393
1,268
Nov 28, 2011
OK, think about what "balancing the bridge" means. It means that there is no voltage across the meter, right?

So the left and right hand sides of the bridge are both voltage dividers, supplied from the same source voltage, VS. The right hand side will divide VS by a fixed ratio, which can be calculated from the two resistor values. This will leave a certain proportion of VS across the 100Ω resistor, and the rest across the 560Ω resistor, right? Can you calculate the proportions of VS that will appear across each of those resistors?

Now you have a voltage divider on the other side as well, and they have told you that when the bridge is balanced, RV is 1232Ω. Can you use the voltage divider formula to calculate what RUNK will be?

3. ### charmcaster.engg

79
1
Mar 20, 2014
I got ratio as 0.178. and the R UNK as 220. Am I right?

4. ### KrisBlueNZSadly passed away in 2015

8,393
1,268
Nov 28, 2011
Yes that's what I get. You've done it an even simpler way than I suggested. It's just all about ratios.