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Guys, the whole website is great! The whole thing is done right!

But need help understanding simulation UI... I have a battery (with a ground) and a wire which does not go anywhere. Run simulate and I get voltage on the wire? https://www.circuitlab.com/circuit/8f5s33/wire-battery-ground/

Ok, now another corner case - let's loop this wire between positive and negative. https://www.circuitlab.com/circuit/c5f295/circuit-battery-ground/ "Unable to get solution"?... Why :(

1st circuit:

Simulate > DC > Run DC Solver

and look at the result for V(un1)

Says N/A before simulation.

Says 1.000V after.

That's correct.

If you add a label to the top end of the wire from the +ve end of the voltage source and call it 'fred' then run the sim again, you will see:

V(fred) 1.000V

To run a DC Sweep, Time Domain (or transient) or Frequency Domain (AC Sweep) sim you will have to enter some values into the sim set up dialogue box.

2nd circuit:

In most simulators - of which CL is an example - a voltage source is an ideal source: it has zero source resistance and can source or sink infinite current.

If you short it through a simulated wire - that has zero resistance - to ground then the simulator is trying to calculate an infinite current.

Simulators cannot do that so they throw an error message.

However, CL's error messages are not as informative as Sir might like.

:)

To get a better idea of how to drive CL, you might like to look at and have a play with some of the other public circuits. Some of the one's from peoples course work, the examples by the authors and some of my own may help you understand more.

:)