How to tell if two points in a circuit have equal voltage

[Aya Elsayed]

It's written in my book that if you have two points having the same voltage then you'll cancel the resistance between them ... how can I know if the voltages of the two points are equal ...( The resistances are given in the circuit .)

 

[phinds]

... how can I know if the voltages of the two points are equal

Analyze the circuit

 

[Aya Elsayed]

Analyze the circuit

In which way?

 

[phinds]

In which way?

Do you know ANYTHING about circuits? Your question is too broad to have an answer.

 

[Baluncore]

if you have two points having the same voltage then you'll cancel the resistance between them

Cancel in that case means you can ignore any resistance between them.
Take a look at the diagram at the top of this page; https://en.wikipedia.org/wiki/Wheatstone_bridge
If the bridge is balanced, V_G will be zero and the resistance of the meter V_G will not have any effect on currents in the circuit. You can then join points D and B with an open or a short circuit without any change.
When balanced the ratio R1/R2 = R3/Rx.

 

[Tom.G]

Here is a short tutorial article about a Wheatstone Bridge circuit. It is sometimes used to measure resistor values. It's operation at least partly describes an answer to your question. Hope it helps. There are other tutorials on the same site that may interest you.

http://www.electronics-tutorials.ws/blog/wheatstone-bridge.html

 

[Aya Elsayed]

Thank you all for help ..got it !