Questions! (1 Viewer)

[Premus]

1. What is the colour of cathode rays ? (when they glow at the anode?)

2. When an electric field is placed across a semiconductor:

A) electrons in the conduction band move in the direction of the field, while holes in the valence band move in the opp direction to the field.

B)electrons in the valence band move in the same direction as the field, while holes in the conduction band move in the opp direction to the field.

C)electrons in the valence band move in the opp direction to the field, while holes in the conduction band move in the same direction as the field

D) electrons in the conduction band move in the opp direction to the field, while holes in the valence band move in the same direction as the field.

3. this is regarding the North and South poles of the Earth. In what direction is the magentic field of the earth going?

Thanks

 

[wind]

1. What is the colour of cathode rays ? (when they glow at the anode?)
Green. It's because of the chemical reaction between the silica in the glass and cathode rays.

2. When an electric field is placed across a semiconductor:
D) electrons in the conduction band move in the opp direction to the field, while holes in the valence band move in the same direction as the field.

3. this is regarding the North and South poles of the Earth. In what direction is the magentic field of the earth going?
South to north.

Edit: Cleared up a mistake.

 

[helper]

Its (D) the electrons in the conduction band, and holes in the valance band.

Eveything else wind said is correct.

 

[Premus]

The answer says 2 is D ....and how do u explain whether they move in the same direction of the field or not?
and for question 3, from memory my teacher said it would be going from south to north (something to do with a compass)...can anyone pls clear this up?

Thanks

 

[wind]

Ohh oops! hahaha...sorry

Just skimmed through the options.

 

[helper]

Sorry thats right Primus, The North Pole of the Earth is actually a South Pole. It is where the north end of a magnet points. So the field goes from the Earth's South Pole to the Earth's North pole.

 

[wind]

I thought it was because the needle pointing to the north is actually magnetically south?

 

[helper]

No its the other way round. One of those stupid history things like current and too hard to change now.

 

[wind]

Alright I'm confused now! hahahah

 

[somborac]

1. What is the colour of cathode rays ? (when they glow at the anode?)

Thanks

its not green...it can be different colors, depends on the gas inside the cathode tube, i seen it be green, blue and purple. hence different flourescent lights

 

[wind]

its not green...it can be different colors, depends on the gas inside the cathode tube, i seen it be green, blue and purple. hence different flourescent lights

He said at the anode.

The actual area of the anode in the CRT fluoresces green because the electrons react with the silica in the glass.

Else where, I'd understand.

 

[helper]

Alright I'm confused now! hahahah

For Earth remember the mag field lines go from S to N. The opposite to what they normally do.

 

[Jase]

AHahhaa Thank GOD! I was thinking about this the other day... with my compass, and im like.."Why the hell does the north end of the compass point towards the north end of the Earth??" it all makes sense now!

This is like when my physics teacher wrote on my paper "no valence electrons", and i thought he mean there are no valence electrons in a semiconductor..... then he said, no .. that said "no." as in number. You had to mention how many electrons are in valence for trivalent and pentavalent elements.. how stupid is that.

 

[smallcattle]

so the north pole is actually a south pole??

 

[Jase]

Yes, the magnetic north pole is in fact a south pole.. but this is going to change in due time, due to crustal movements of some sort.. so one day, someone's out in the bush... their compass will suddenly switch to the other side. ahhaha.