Physics help

[werto165]

Basically an emf is a voltage and I'm not entirely sure how it works, voltages are induced in coils if there is a change in flux linkage, would it be right to say that the steel string cuts the magnetic field of the coil this in turn produces a changing flux and therefore a emf? Or am I missing something entirely?

[C_Mike]

The steel wire vibrating cuts through the magnetic field generated by the coil. 

 

This causes a change in Magnetic Flux. 

 

Since Emf = Change In Magnetic Flux / Change In Time

 

And EMF is induced.

 

How many marks is the question worth, that will help determine how many points are needed

[werto165]

The steel wire vibrating cuts through the magnetic field generated by the coil. 

 

This causes a change in Magnetic Flux. 

 

Since Emf = Change In Magnetic Flux / Change In Time

 

And EMF is induced.

 

How many marks is the question worth, that will help determine how many points are needed

4 marks. but its QWC( quality of written communcation is 1 mark) so most likely 3 points.

[werto165]

I found the mark scheme:

C_Mike

Steel has a high permeability/higher than air ORA (1)

Changing air gap between wire and magnet (1)

The permeance of the magnetic circuit changes as the

steel moves (1)

This changes the flux (linkage in the coil) (1)

A change in flux (linkage) produces an emf (in the coil) (1)

4

Do not credit change of flux experienced by wire cutting

through field or emf induced in wire.

 

So probably 2 marks for what I wrote.

[C_Mike]

 

I found the mark scheme:

@C_Mike

Steel has a high permeability/higher than air ORA (1)

Changing air gap between wire and magnet (1)

The permeance of the magnetic circuit changes as the

steel moves (1)

This changes the flux (linkage in the coil) (1)

A change in flux (linkage) produces an emf (in the coil) (1)

4

Do not credit change of flux experienced by wire cutting

through field or emf induced in wire.

 

So probably 2 marks for what I wrote.

 

 

That seems very, very specific. Which Exam Board are you doing this with, I'm assuming this is A-Level

[werto165]

That seems very, very specific. Which Exam Board are you doing this with, I'm assuming this is A-Level

Yep OCR, they're so nit picky at times.