HSC 2005 Question 15. (1 Viewer)

[Divinity_]

Can someone explain the question. Answer is C.

 

[helper]

Apply right hand rule.

electrons first:
Thumb into of page (opposite to current, so flowing out of page but then need to point into because electrons are negative)
Fingers left to right magnetic field
Palm forces electrons down

Holes
Thumb into page (effectively positive charges that travel in direction of current)
Fingers left to right magnetic field
Palm forces electrons down

 

[Divinity_]

Thanks, LOL got confused with conventional current @_@;;

 

[untouchablecuz]

Can someone explain the question. Answer is C.

by the right hand palm rule, the force will be acting downwards and thus the horizontal component of the velocity will not be altered. compare this to projectile motion where the the weight force constitutes the net vertical downward force; as we know, the horizontal component of the velocity will remain constant. in this case, the net downward force is the magnetic force+weight force.

this rules out A and B

because the magnetic force acts vertically, it'll cause the electrons to move down towards the bottom side of the semiconductor rod. you would expect the holes to move to the opposite side because they are "positive" but this is not the case because their movement is only an APPARENT movement. they APPEAR to move backwards as the electrons occupy new holes. .'. they move to the same side

hence, answer is C

 

[darkchild69]

So, this question was in 2005? This is really dealing with the hall effect, so to speak, which was taken out of the syllabus after 2001.

I'll just answer for the sake of answering, even though it has already been answered by the previous answerees

However, using F = qv x B

Holes and electrons move in opposite directions, but they have opposite charges

Left hand for electrons (left thumb out of page)

- Force = down

Right hand for holes (right thumb into page)

- Force = down

Both experience a force in same direction