

Explanation
a) Differences between a d. c. generator and a moving coil galvanometer.



D. C. generator
moving coil galvanometer


converts mechanical energy to electrical energy
converts electrical energy to mechanical energy.


uses split rings or commutator
uses hair springs.


rotation of coil is continuous
rotation of coil is incomplete


uses carbon brushes (as terminals)
uses jeweled bearings (as terminals)



(b) Eddy currents are currents induced in a conductor when subjected to varying magnetic field.   
Any valid additional information e.g.

eddy current flows in a circular path or closed loops;
eddy current generates heat;
eddy current cannot flow through gaps or slots;
The currents move in such a direction as to oppose the change producing them.

Devices in which eddy currents are applied

pointers of sensitive electric meters
sensitive mass balances
brakes in large electric motors
speedometers in automobiles
detection of cracks in railway tracks
detection of metals

(c) Principle on which a potentiometer is based
When a steady current is allowed to pass through a uniform wire, equal lengths of the wire will have equal potential differences.
 OR
The p.d across a length of a wire is (directly) proportional to the length provided the wire has a uniform cross section.
(d)

 Vector diagram showing
 V\(_L\) with arrow
 V\(_C\) with arrow
 V\(_R\) with arrow

(i) V\(^2\) = V\(_R^2\) + (V\(_L\) - V\(_C\))\(^2\) 

 110\(^2\)  = 80\(^2\) + (40 – V\(_C\))\(^2\)
(40 – V\(_C\)) = \(\sqrt{(110 + 80) (110 – 80)}\) 
 40 – V\(_C\) = + 75.5
 V\(_C\) = 40 + 75.5
 V\(_C\) = 115.5V
  
(ii) X\(_c\) \(\frac{V_c}{I} = \frac{1}{2 \pi f c}\)
C = \(\frac{1}{2 \pi fV_c}\)
C \(\frac{2}{2 \times 3.14 \times 60 \times 115.5} = 45.9\muF\) 

(iii) \(V_L = IX_L = I \times 2 \pi fL}\)
L = \(\frac{V_l}{I \times 1 \times 2 \pifVc}\)
C = \(\frac{2}{2 \times 3.142 \times 60 \times 2}\)
= 0.053H

