A constant current flows in the solenoid. Coil C is moved through the solenoid from position X to position Y. On Fig. 6.2, sketch a line to represent how the magnetic flux linkage in coil C changes with position during the movement from X to Y.
Explain the shape of the line you drew in (a)(i).
Coil C is now fixed at X. The current in the solenoid changes so that the magnetic flux density $B$ at X varies from time $0$ to time $4t$ as shown in Fig. 6.3. Calculate the maximum magnetic flux linkage in coil C.
On Fig. 6.4, sketch a line to represent the induced electromotive force (e.m.f.) $E$ in coil C from time $0$ to time $4t$.
A metal spring is lying on a smooth table. Its turns are evenly spaced. The two ends of the spring are connected to a d.c. power supply, as shown in Fig. 6.5, using flexible leads. The spring is not stretched. Referring to magnetic fields, describe and explain how the separation between the turns changes when the power supply is first switched on.