# D1 Use Electrical Circuit Concepts Flashcards

How do you get average value of current?

Eav = 0.637 x peak value (Im)

How do you get effective value? (E or I)

E is equal to 0.707 x peak value (Em)

I is equal to 0.707 x peak value (Im)

How do you find peak value from RMS?

To find peak value from RMS:

ERMS x 1.414(90• sine) = peak (Em)

ERMS / 0.707(45• sine) = peak (Em)

ERMS = Em x 0.707

What is RMS and what is it’s formula

RMS=Root mean square, the power in a resistor is directly proportional to the square of the current or voltage:

P = I*2R P = E*2/R

- = squaring

List all six effective resistances

*hint* S-H-R-E-D-O

Skin effect Hysterisis loss Radiation loss Eddy currents Dielectric loss Ohmic resistance in pure form

What is the skin Effect?

Skin effect:

Most current flows on the outer surface of the conductor. The expanding and contracting lines of force in a conductor are most dense at the center and as such push the current to the outside of the conductor. This is the same as reducing the cross sectional area of the conductor and this effectively increases it’s Ohmic resistance value

The Higher the hertz (Hz) the more extreme the effect

What is Hysterisis loss?

Hysterisis loss, as AC frequency is constantly. Changing the magnetic domain, the direction is constantly being reversed, this creates an energy loss in the form of heat

What is Eddy current loss?

Eddy currents,

The core of the magnetic field acts like a conductor and has currents induced within it, these are called eddy currents

( 1Tesla)

What is Dialectric loss?

Insulating material exposes to and electric field is referred to as a Dialectric. When voltage is applied against a dielectric and this results in a heat loss, this heat is generated from the circuit.

What is radiation loss?

Radiation losses, at higher frequency some of the magnetic lines of force escape from the conductor and do not return, these lines of force are energy, this energy loss results in a higher effective resistance.

What is Ohmic resistance in pure it’s pure form?

What is it’s formula?

Pure Ohmic resistance, as the conductor heats up due to it’s positive temperature co-efficient it’s effective resistance goes up

(R= P/I*2)

*means squared

What is the formula for factors affecting inductance?

L= N*2uA/ &

L= inductance N= Number of turns in the coil u= permeability of the core material in webers per ampere turn in metres. &= length of the core in metres.

How do you get instantaneous voltage? (e)

e =Em x Sine angle theta degree

What is Faradays law of electromagnetic induction?

Faradays law of electromagnetic induction:

B= flux density in Teslas L= active Length in meter form V= velocity meter per second E= Voltage generated in volts

E= BLV L= E/BV B= E/LV V= E/BL

What is the time constant formula?

Time constants

During each time constant, the current increases by 63.2% of the difference between it’s starting value and steady state. After five time constants (¥), the current reaches 99.3% of steady state value. Achieved after five time constants

¥= length of one time constant in seconds L= inductance of the circuit in Henries R= Resistance of the circuit in Ohms

¥= L/R

¥= *not symbol for the Greek letter Tau*