30-03-2013, 01:43 PM
Yes, in a closed system energy is conserved.
It's not usually a good idea to invoke conservation of energy, when trying to calculate things - because it's easy to overlook an energy conversion mechanism (such as this one) - energy turned into heat, or turned into EM radiation, according to whether you consider a linking resistance which tends to zero, or an inductor with dimensions which tend to zero.
The situation is a bit like a 20 ton railway truck, trundling along a line at 10mph, which collides with a stationary truck also 20 ton, which couple together. The combined affair has 40 ton mass and carries on at 5mph (easily calculated using Conservation of Momentum), but if you work out the initial and final kinetic energies ½mv², you've lost half the KE in the process.
It's not usually a good idea to invoke conservation of energy, when trying to calculate things - because it's easy to overlook an energy conversion mechanism (such as this one) - energy turned into heat, or turned into EM radiation, according to whether you consider a linking resistance which tends to zero, or an inductor with dimensions which tend to zero.
The situation is a bit like a 20 ton railway truck, trundling along a line at 10mph, which collides with a stationary truck also 20 ton, which couple together. The combined affair has 40 ton mass and carries on at 5mph (easily calculated using Conservation of Momentum), but if you work out the initial and final kinetic energies ½mv², you've lost half the KE in the process.
