Answer:
(a) The self inductance, L = 21.95 mH
(b) The energy stored, E = 4.84 J
(c) the time, t = 0.154 s
Explanation:
(a) Self inductance is calculated as;

where;
N is the number of turns = 1000 loops
μ is the permeability of free space = 4π x 10⁻⁷ H/m
l is the length of the inductor, = 45 cm = 0.45 m
A is the area of the inductor (given diameter = 10 cm = 0.1 m)

(b) The energy stored in the inductor when 21 A current ;

(c) time it can be turned off if the induced emf cannot exceed 3.0 V;

Answer: 0.6m
Explanation:
Given that:
force = 4.5 N
Work done = 2.7J
Distance moved by the book = ?
Since work is done when force is applied on an object over a distance, apply the formula:
work = force x distance
2.7J = 4.5N x distance
Distance = (2.7J / 4.5N)
Distance = 0.6 m
Thus, the book was moved 0.6 metres far
Answer:
The dimensional formula of Young's modulus is [ML^-1T^-2]
The fraction of energy that is lost is 25%, it depends how fast the ball was going until it lost 25% of its energy, the gravitational energy was transferred into the kinetic energy that helped the ball bounce back