inductors

Question 1

when looking at a diagram depicting current what do arrows and crosses represent

Answer 1

cross: current flowing into the page
dot: current flowing out of the page

Question 1

method to determine the direction of magneto flux

Answer 1

right-hand rule

Question 2

what is reluctance in a magnetic circuit

Answer 2

its the equivalent to resistance in electrical circuits

Question 3

define saturation

Answer 3

the point at which adding current has no significant effect on magnetic flux

Question 4

reluctance (Re)

Answer 4

= l / μA

*length (l)
*cross-sectional area (A)
*permeability of magnetic material (μ)

Question 5

inductance (L)

Answer 5

= Nφ / i
= N^2 / Re

units: Henry

*no. of turns (N)
*magnetic flux (φ)
*current (i)
*reluctance (Re)

Question 6

induced voltage (emf)

Answer 6

= rate of change of ‘flux linkage’

= L di/dt
= N dφ/dt

*inductance (L)
*rate of change in current (i)
*no. of turns (N)
*rate of change in magnetic flux (φ)

Question 7

energy stored (W)

Answer 7

= 1/2 LI^2

*inductance (L)
*current (I)

Question 8

flux density (B)

Answer 8

= φ/A

*magnetic flux (φ)
*cross-sectional area (A)

Question 9

current in a circuit with an inductor and a resistor

Answer 9

i = Vo/R (1 - e^-t/τ)

*resistance (R)
*time (t)
*voltage (Vo)
*time constant (τ)

Question 10

time constant (τ)

Answer 10

= L/R

*resistance (R)
*inductance (L)

Question 11

voltage across inductor in a circuit with an inductor and a resistor

Answer 11

= Vo (e^-t/τ)

*time (t)
*voltage (Vo)
*time constant (τ)