Very quick noob Edexcel PHY5 question!

The markscheme is wrong. If the current goes upwards at the top the hub is positive and the rim negative.

The problem is that I used the right hand rule and the markscheme did not concur!

Exactly, me too, which is why you should use the left hand rule (however wrong it may be) to get the right answer.

Haha how on earth did you manage that? You must be good at hand gymnastics.

But it is only 1mark and you have a 50% chance of getting it right if you don't have a clue what you're doing lol.

what fingers represent what?

Thumb is the motion, Index finger is the field, Second finger is the direction of the induced conventional current. (for both left and right hand rules)

Right hand rule deal with conventional current. This is the current that the world of physics uses because some victorians guessed wrong - the actual flow of electrons is opposite to the conventional current. So yes, the hub is negative and the rims is positive.

so, on the right hand at the top, index finger pointing into the page, thub goiing right, middle finger is upwards, so electrons go downwards, hub is negative.

what am i doing wrong?

If the current is up, current is defined as the movement of positive charges. Therefore it must be away from positive and towards negative right? So wouldn't a current moving upwards suggest that the hub is positive and the rim is negative?
I think your explanation would be right if the circuit was not closed, and an accumulating charge forms on the hub, but it says that a constant emf is generated, implying a closed circuit?

?? no, if current is up, movement of electrons is down. the emf is caused by this movement of electrons, the electrons are not responding to an emf that is already present.

as you said, current is movement of positive sharges. current is up, so the top is positive.

Okay, I see what you mean. Negative charges accumulate at the hub, since positive charges cannot move and electron movement is opposite to current. THANKS . My goodness, that took a while to clear up

Okay so e.m.f. refers to the opposite charges on the electrodes, compared to conventional current?

Conventional e.m.f. is consistent with conventional current. The actual electron movement is in the opposite direction, as is the direction of the internal electric field caused by the movement.