Physics unit 4 exam questions

[TheRajinator]

Could someone explain:
vcaa 2010 exam:

electric power: Q3 how do we know which side of the solenoid is north and which side is south when the solenoid isn't connected to the circuit.

[availn]

It is using the same solenoid from figure 1.

[TheRajinator]

But that would mena the force is acting upwards as the current is going from Q to P and the madnetic field is going from left to right. hence using right hand slap rule the force would be upwards. but the answer is downwards

[availn]

The magnetic field is going from right to left, not left to right.

[TheRajinator]

It's okay I see what I did wrong. Magnetic field outside is going from left to right, but inside the solenoid the magnetic field is going from right to left. because the coil is inside the solenoid the magnetic fielf from right to left applies. Am I right?

[TheRajinator]

Also for Q2 of light on the same exam, how does the wave model explain observation 1 and 3?

[availn]

It's okay I see what I did wrong. Magnetic field outside is going from left to right, but inside the solenoid the magnetic field is going from right to left. because the coil is inside the solenoid the magnetic fielf from right to left applies. Am I right?

Also for Q2 of light on the same exam, how does the wave model explain observation 1 and 3?

Yep, it is easier to think of the B field in solenoids as continuous loops, rather than it having a north and south (which is does), as the field inside a solenoid will go from south to north.

As for Q2, here are my thoughts, but I'm not fully sure.
If light is a wave, it delivers energy to the electrons constantly and cumulatively. Therefore, more light results in more energy, which will result in more photoelectrons.
A certain amount of energy is needed to free an electron. This amount of energy would differ depending on the metal surface (this observation has nothing much to do with either the particle or wave models of light).

[TheRajinator]

yea that makes sense, thanks

[TheRajinator]

is the centeral maximum 2x for double slit or single slit?

[TheRajinator]

For side AB on a coil where AB is parallel to the magnets, would the force on it always be constant as it is always 90 degrees to the magnetic field? so when do we apply the formula F=nBILsin(theta)??