Trouble working out values in circuit

I'm having serious trouble working out the values for Voltage at A,B,C and the current at i5, i4 and i1. Could anyone please help me?

by desm0nd
November 02, 2018

The total voltage around the loop is 12V-6V=6V.

The total resistance is 20+10+15+20//25.

Hence i1.

i4+i5=i1

20i4=25i5.

Hence i4 and i5.

Voltages: where is 0V?

by mikerogerswsm
November 02, 2018

I'm not too sure where 0V is as it doesn't say on the diagram I have been given. Here's a link to the actual diagram and question I have been given

http://tinypic.com/r/2e5m6nr/9

Many thanks for your help.

by desm0nd
November 03, 2018

That link doesn't seem to work.

by mikerogerswsm
November 03, 2018

Vba=i1.R2+6V

Vca=Vba+i1.R3

by mikerogerswsm
November 03, 2018

Link worked once then stopped again.

by mikerogerswsm
November 03, 2018

Link works when you click on Zoom.

The points A B and C are shown but there is no indication of a 0V point.

Therefore I have assumed A to be reference and have worked out Vba, ie voltage at B with reference to A, and Vca, which is the voltage at C with reference to A.

This does seem to be a misleading question, much better to have a line at the bottom representing 0V. Physics teachers always seem to get circuits wrong. To electronics folk + is up. Much more rational.

by mikerogerswsm
November 04, 2018

Another problem with the circuit in the link is the use of bidirectional arrows to indicate current. Much better to use one arrow, then the current in that direction is either positive or negative, making the solution to other parts of the problem easier.

Please feel free to show my comments to your headmaster. He may decide to seek a better teacher for you.

by mikerogerswsm
November 04, 2018

Power dissipated = I1^2.(R1 + R2 + R3) + I4^2.R4 + I5^2.R5

Where ^2 means squared.

by mikerogerswsm
November 04, 2018

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