Chapter 9: Inductors

Lenz's Law

The direction of an induced current is such that it'll oppose the change causing it.

Inductance

The property of a conductor to oppose a change in current flowing through itself.

self inductance (L)

The property of a wire, either straight or in a coil, to create an induced voltage that opposes the change in the potential difference across the wire.

In a RL series circuit, when switched to a DC voltage source, the Vr looks like?

a rising exponential

what are the (4) common types of inductors?

1. Encapsulated 2. Wirehound, high current 3. Torroid coil 4. Variable

what (5) factors affect inductance?

1. Inductance in Henries (H) 2. # of turns of wire (N) 3. Permeability in H/m or Wb/At-m (micro) 4. coil length in meters (l) 5. Area

what (2) physical parameters affect a practical inductor?

1. Winding resistance (Rw) 2. Winding capacitance (Cw)

Parallel Inductance

1/Lt = 1/L1 + 1/L2 + ...

what is the inductance if a 37mV is induced across a coil if the current is charging at a rate of 680mA/s?

L = .054H

what is the inductance of a 2cm long 150 turn coil wrapped on a low carbon steel core that is .5cm in diameter? the permeability of a low carbon steel is 2.5*10^-4 H/m

L = 22mH

Series Inductance

Lt = L1 +L2 +...

If a 1.5mH inductor is connected in parallel with a 680microH inductor, Lt=?

Lt=.468mH

If L1=270microH, L2=1.2mH, connected in parallel, Lt=?

Lt=0.22mH

If L1=270microH, L2=1.2mH, connected in series, Lt=?

Lt=1.47mH

If a 1.5mH inductor is connected in series with a 680microH inductor, Lt=?

Lt=2.18mH

when the field is building, the final current is ____ than the initial current

greater than

when the field is collapsing, the final current is ____ than the initial current

less than

Assuming all other factors are the same, the inductance of an inductor will be larger if ?

more turns, larger area, length is shorter

the henry is defined as the inductance of a coil, when?

one volt is induced due to a change in current of 1A/s