elctricity?

Question

1) If any apparatus placed with in a hollow charged metal enclosure, why is it shielded from elctric field?

2) we always connect a negative terminla with a positive terminal right? or not?

Answer 1

1) metal is a good conductor of electricity, and when charges are placed inside a conductor, they tend to spread out so that there's an even charge distribution. since the object inside the metal enclosure is surrounded by charge on all sides, the electric field vectors from the charged metal enclosure cancel out on the inside. therefore, there is no electric field inside the metal enclosure.
2) yes, it's true that electricity flows from regions of high voltage to regions of lower voltage. but if you attach a negative terminal to a positive terminal without putting some electrically-powered devices in between, you'll end up frying your battery really fast.

Answer 2

1) Reflection and absorption are two principle shielding mechanisms. When an electromagnetic wave traveling through space encounters a shield, two things happen. First, much of the energy is reflected, as shown in Figure 11. Second, some of the energy not reflected is absorbed by the shield. Only the residual energy emerges from the other side of the shield. These two effects of reflection and absorption are independent, but they combine to give the overall shield effectiveness.

A third factor, called re-reflection, occurs in very thin shields. This is also shown in Figure 11. This secondary reflection occurs at the shield boundary on the far side of the shield material. This factor is fairly minor and is often ignored.

2) If you want the circuit to work, your statement is true, but taking the question literally, in life I am sure there are people (including myself) who have connected a negative to negative or positive to positive.

Answer 3

1) the metal surrounding the apparatus is like an antenna that catches RF. Normal situations like this are grounding one end of a shielded (A/V) cable to prevent RF interference from entering the cable (and becoming a nuisance like static noise or lines on the TV screen)

2) To connect DC batteries in series (where their voltages add to each other), connect the batteries Neg. to Pos.

Answer 4

This is so because availability of free negatively charged particles electrons make the metal to be always at same potential throughout inside the metal, causing it to be equi-potential. In other words elcetric field inside conductor is always zero.

We connect + ve to negative to make th ecurrent flow in a circuit on a permanent basis.