# physics

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1)Two metal spheres are suspended from insulation threads. A negatively charged rod is brought near these spheres. One shere is pushed away from the rod and the other atracted towards it. Describe the behavior of the spheres.

I know one has to be negative and the other positive but I don't know what else they're looking for.

2)The electricity received at an electric substation has a potential difference of 2.80 x 10^5 V. If the required output is 440 V, what should be the ratio of the turns of the step-down transformer?

I know the transformer equation is:

Is/Ip = Vp/Vs = Np/Ns

Thats the closest thing I could find regarding this problem

• physics - ,

2. Use that equation to get the turns ratio Np/Ns

1. The sphere repulsed is negative. The attracted sphere could be neutral, or positive. If neutral, what is happening is that electrons on the surface are repulsed, and move to the opposite side, leaving a net positive side on the near side. Since the net positive side is closest, it has more force of attraction than the negative side further away, so it is attracted.

• physics is this it? - ,

so it would be:

Vp/Vs = Np/Ns
(2.80 x 10^5)/(440)

I'm not sure on the values