The voltage across the solenoid is given by the rate-change of the flux times the number of loops: Therefore, the
inductance Longer solenoids and
solenoids with more cross-sectional area have more
inductance. The strongest dependence is on the number of
turns per unit length. One can also increase the
inductance by using iron instead of a vacuum. One would
replace the parameter We have now considered three circuit elements (aside from batteries). The voltage across each element depends on a different aspect of the charge. Capacitors: (1/**V =**) Q**C** The voltage drop across the capacitor is proportional to the charge on the capacitor.Resistors: =**V****R****I**The voltage drop is proportional to the current, which is the rate-change of the charge.
Inductors: =**V**(**L****D**/**I****D**)**t** The voltage drop across the inductor is proportional to the rate-change of the current.
A resistor keeps the charge from changing instantly in a circuit, because an instant change in the charge constitutes an infinite current which implies an infinite voltage. Similarly, an inductor keeps the current from changing suddenly. Unlike a capacitor, current can continuously flow through an inductor. An inductor can also store energy. The power being stored in an inductor is: A little calculus would show that the energy stored in an inductor is: |