Acircular coil of wire of radius 8 cm and 19 turns is placed with its plane perpendicular to a 5.6 t magnetic field, produced by an electromagnet. the current to the electromagnet is then switched off, causing the magnetic field to collapse to zero in a time of 744 ms. what is the emf generated in the coil while the magnetic field is collapsing, in units of volts?

2.87 Volt

Explanation:

N = 19

change in magnetic field = 5.6 T

Time, dt = 744 ms = 0.744 s

Induced emf,

e = N × change in flux / time

e = 19 × 3.14 × 0.08 × 0.08 ×5.6/0.744

e = 2.87 Volt

when it gains or loses electrons

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me