# Recent content by Stonebridge

1. ### What directions do the current and electric field point if the electrons move right?

Yes, the electric field is to the left, in the same direction as the positive charges move. You can apply an external electric field perpendicular to a beam of electrons, for example, if you want to deflect them. This is exactly what is done in an oscilloscope to deflect the beam of electrons...

3. ### What directions do the current and electric field point if the electrons move right?

The RHR is for finding the direction of magnetic fields. If electrons move to the right then conventional current, which is a flow of positive charge, moves to the left. The direction of the electric field is the direction of the force on a positive charge. That is, in this case, the direction...
4. ### Damped oscillator consecutive amplitude ratio

This is useful http://en.wikipedia.org/wiki/Logarithmic_decrement
5. ### When you can't use conservation of energy

Indeed. I could have added that in questions of this type, it's whether or not you can consider mechanical energy to be conserved.
6. ### When you can't use conservation of energy

It depends what you have done. If you can show us how you attempted to solve the problem it would help. The exact wording of the question is also important. Questions like this usually say things like "ignore friction" as a clue to being able to use conservation of energy. Energy can take a...
7. ### Varying pressures

Yes that's correct.

9. ### Effective Resistance if bent in the form a circle

It's because it is equivalent to having two resistors in parallel. The current entering at A has a choice of 2 directions. Both involve taking a path that is 4R. That is, half the resistance of the complete wire. (Round half the circumference to B.) So to find the combined resistance, you need...
10. ### Proving Optical Law in plane mirror

You have actually already proved it. You have proved that the image of point A is at the point marked a and that this point is -behind the mirror -equidistant -in the position shown Now do the same for any other point on the object and you will find the same result. All points on the object...
11. ### Size of cavity on expansion

Imagine a circular metal plate on which you have drawn a chalk circle about half way between the centre and the rim. Heat the plate. Does the chalk circle expand or contract? Now cut out a hole in the plate marked out by the chalk but with the chalk line just visible. Heat the plate. Does the...
12. ### Grounding/earthing in a simple circuit

Yes. The potential of the left side of the circuit will be +0.5V and the potential of the right side of the circuit will be -0.5V This gives a potential difference of 0.5V - (-0.5V) = 1V
13. ### Grounding/earthing in a simple circuit

No it doesn't affect the voltage drop (pd) across the two resistors. What it does do is to set the potential of the point between the two resistors at zero. To the left of the left R the potential will be positive and to the right of the right R the potential will be negative.
14. ### Augustine in septic tank (Alice in Wonderland)

Yes that's fine now.
15. ### Orbit of Moon and the earth around thier COM

The moon's orbit is not regular. There is a perigee and apogee whereby the distance between the Earth and Moon varies considerably during its orbit. This in turn means the distance of both Earth and Moon from the CoM varies. The c of m is in orbit about the Sun which gives rise to a slight...