Inductors

What are two ways to decrease the winding resistance of a coil?

1. Reduce the number of turns 2. Using a larger wire

When inductors are connected in parallel, the total inductance

1/LT = 1/L1 + 1/L2 + 1/L3 + ... + 1/Ln

Four 10mH inductors are in series. The total inductance is

40mH or 40,000 uH

T/F: If a series RL circuit is connected to a DC source, the maximum current is limited by the total inductance.

False The maximum current is limited by the time constant. Inductance (L) is in henries and Resistance (R) is in ohms. t=L/R

Device that stores energy in a magnetic field

Inductor

A 1mH, 3.3mH and a 0.1mH inductor are connected in parallel. Thus the total inductance is

Less than the smallest inductor = 0.1mH exact answer is 0.088mH

When the current through an inductor doubles, the stored energy____

Quadruples

The inductance of an iron-core coil increases if

The number of turns is increased

An ideal inductor has no

Winding Resistance

The formula for the time constant of an RL circuit

t = L/R

An inductor, a resistor and a switch are connected in series to a 12 Volt battery. At the instant the switch is closed, the inductor voltage is

12 volts

The ________ reaches 1% of its initial value in approximately 5t;

Current

_____ law states that relative motion between a magnetic field and a coil induces a voltage across the coil.

Faraday's Law

When the current through an inductor increases, the amount of energy stored in the electromagnetic field_____

Increases

Voltage produced as a result of a changing magnetic field.

Induced Voltage

Characteristic of an electrical conductor that opposes a change in current flow

Inductance

______ law states that the polarity of induced voltage results induced current in a direction that opposes the change in the magnetic field that produced it.

Lenz's Law

In a series RL circuit, the current will increase to _________________ of its full value in one time constant (t) interval after the switch is closed

approximately 63%

When inductors are connected in series, the total inductance

increases LT = L1 + L2 + L3 + ... + Ln

Opposes the change in current

induced voltage

The total inductance in parallel, is always less than

the smallest inductor

When there is constant (DC) current in an inductor:

there is no induced voltage