How Does a Moving-Coil Galvanometer Measure High Voltages and Currents?

[Mazaraika]

Homework Statement

a moving-coil gavanometer consists of a coil that is free to rotate between the poles of a permanent magnet. the magnetic field strength between the poles is 5 x (10^-2) T. The coil consists of 250 loops of copper wire, diameter 0.5 mm, wound to form a square coil, with an average side length of 2.5 cm. At full-scale deflection, the plane of the coil makes an angle of 60(degrees) to the magnetic field and the torque on the coil is 40 uNm. You can assume that all of the resistance of the gavanometer comes from the coil. Resistivity of copper= 1.7 x (10^-8) Ohms m

i). how can this instrument be adapted so that it can be used to measure potential differences up to 20V?
ii). how can it be modified to measure currents up to 1 A?
iii). What, briefly would be the effect on the sensitivity of the instrument (i.e the current required in the coil to give full-scale deflection) of putting a soft iron core in the centre of the coil? justify your answer
b). what would be the resistance of an ideal voltmeter and an ideal ammeter? briefly explain your answers.

(Ive attached the question paper, named WOE Coursework 2)

Homework Equations

i didn't know where to start, and which equations i was meant to use, as the resistance and current, or voltage isn't given. (attached notes on it, named part 4 and part 5)

The Attempt at a Solution

again didnt know where to start :(... Neeed help with working out so i understand it, thanks a lot. (you can use the attached notes to help you understand better), and its in for tomorrow so would really be appreciated if you gave an answer, working out and explained it.

 

[Mazaraika]

bump

(also attached another set of notes which may be of further help)

 

[Mazaraika]

need help bump bump

 

[Mazaraika]

Ive managed to work out part i). and ii). just need help with part iii). and b). and questions 2 and 3 now :)