|
As we have seen, inductance makes it harder to change the current flowing in a circuit.
The circuit shows the symbol for an inductor. When the power supply is first switched on, the inductor prevents the current from rising immediately to the final value. Instead, the current tends exponentially to I0. This is similar to the way the voltage increases across a capacitor.
Eventually, when the current is no longer changing, there is no longer any EMF across the inductor. In the steady state, the circuit behaves as though the inductor were not there! The inductor only opposes changes in the current.
We may see this again if we short out the power supply once the steady state has been reached. The inductor does not allow the current to fall to zero immediately! Instead, the current decays slowly. The rate of decay is the same as the initial rate of increase:
Inductance in a circuit can be annoying! In many situations, it is desirable to be able to switch the current on and off very rapidly. This is the case in computers and many other electronic devices.
However, it can also be very useful. Inductors can be used to make resonant circuits and signal filters.
|
A straight wire of length L is travelling at velocity v m s-1 in a direction perpendicular to a magnetic field of strength B. What is the EMF generated between the ends of the wire ? Apply your result to find the EMF generated between the wing-tips of an aircraft (48 m apart) flying at 640 km h-1 due to the Earth's magnetic field (whose vertical component is 0.6 × 10-4 T).
|
|
A coil of resistance 3.5 Ω has a steady current of 0.2 A flowing through it. The coil is then shorted, and the current decay is measured. After 0.12 s the current has fallen to 0.1 A. What is the inductance of the coil ?
|
|
An electronic component has a resistance of 25 Ω and an inductance of 3 mH. If the potential difference across the component is suddenly increased from 0 to 2 V, how long does it take for the current to reach 0.03 A ? If this operation constitutes one cycle, how many cycles per second is the component capable of ?
|
|
