How to balance the bridge?

[charmcaster.engg]

In the given circuit, what is RUNK equal to if RV must be adjusted to 1,232

in order to balance the bridge?

 

[KrisBlueNZ]

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, V_S. The right hand side will divide V_S by a fixed ratio, which can be calculated from the two resistor values. This will leave a certain proportion of V_S across the 100Ω resistor, and the rest across the 560Ω resistor, right? Can you calculate the proportions of V_S 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, R_V is 1232Ω. Can you use the voltage divider formula to calculate what R_UNK will be?

 

[charmcaster.engg]

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, V_S. The right hand side will divide V_S by a fixed ratio, which can be calculated from the two resistor values. This will leave a certain proportion of V_S across the 100Ω resistor, and the rest across the 560Ω resistor, right? Can you calculate the proportions of V_S 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, R_V is 1232Ω. Can you use the voltage divider formula to calculate what R_UNK will be?

I got ratio as 0.178. and the R UNK as 220. Am I right?

 

[KrisBlueNZ]

Yes that's what I get. You've done it an even simpler way than I suggested. It's just all about ratios.