Electrical

Question 1

What are copper losses

How to show them

Answer 1

Power loss due to reisstance in windings + leakage of inductance in windings

Series resistor Inductor (draw diagram)

Question 2

What are iron losses

Answer 2

Losses due to hysterics , eddy currents, and loss in flux

Parallels inductor and resistor

Question 3

How to measure copper loss

How to measure iron loss

Answer 3

Shirt circuit test, impedance federal and the. Use the rated current and powers (disregard the iron loss )

Open circuit test , (disregards copper loss) and use rated voltage along with power

Question 4

Why cmos better than nmos 2 points

Answer 4

Only consumes power when switching stats

But only transistors, no need to use any resistors so much smaller

Question 5

thevinin theroem

Answer 5

as far as load is concerened, a linear circuit may be represented by an ideal voltage source Vth in series with a resistor Rth,

where VTh is Voc and RTH is Voc/ Isc

Question 6

norton theroem

Answer 6

as far as load is concerned, a linear circuit can be replaced by an ideal current source IN in parallel with a resistor RN

where IN is given by Isc and RN Voc/ Isc

no load = not possible + can do thev / norton to the entire circuit at once

Question 7

ideal opamp assumptions (3)

Answer 7

• infinite open loop gain A
• infinite input impedance
• 0 output impedance

Question 8

why is it assumed for metallic conductors that there any net charge is distributed on the surface only

Answer 8

by gauss law, if there were any charge inside the conductor there would be an electric field, which would casue such charges to surface of the conductor , such that the internal net electric field would become zero

Question 9

self inductance defined

Answer 9

fluz linked of cicuit / current

Question 10

method for capacitance

Answer 10

1) make inner circle a +q, and +v, outer -q and ground, then its really easy

Question 11

purpose of source follower

Answer 11

high input impedance low output impedance and drives high current, so expect r2 to be much smaller

Question 12

assumptions for flux conservation

Answer 12

no fringing effects , distance too small

Question 13

virtual work derivation

Answer 13

in order to maintain electrostatic equilibroum a force is acted on the two charged objects
moving a charged object
- attractive force F is balanced by restoring force -F which we want to find.
- this does mech work -Fdx
- requires work from battery v dq ( use voltage equation is w/q)
- and results in a change of electrostatic energy 0.5 VQ (area under qv grah)
- equate and differntiate

Question 14

why does virtual work show that only the force depends on mutual inductance

Answer 14

this becasue the self inductance terms are definitely constant, so it must depend on the Mi1i2 term only

the only change in energy as vf is dw/dx is due to M which changes with x

Question 15

max power output transfer thereom for amplifiers

Answer 15

is v out sqaured/ rL, or better I sqaured RLdifferentiate wrt to Rl set to 0, happens when RL= R total output impedance

Question 16

what are coupling and bypass caps used for in amplifiers

Answer 16

c1 coupling prevents the dc component of the output from the preivous circuit from entering so it doesnt mess up the dc biasing and c2 blocks its own dc

cs is a bypass capacitor that tries to increase the gain which is limited by vs, but vs is needed to bias the circuit. at dc f is low so open circuit but when ac f is high then short

Question 17

how does tuning work

Answer 17

one frequency is chosen to be amplified whilst the rest attenuated. hence capacitance and inducantce chosen so that at specific f it will go to resosnance cancelling these terms leaving resisitive only an dgain hella high

so at tuning selected f is resonance

Question 19

What does 2s complement mean

Answer 19

Us a coding of binary number that allows representation of negative numbers for an 8 bit word

0-127 are the positive range = which is the same as unsigned
-128 to -1 is the negative range

• the negative numbers are converted to 2s complement by inverting snd adding 1

Question 20

Significance of 2s complement

Answer 20

Normal binary arithmetic csn be used , no separate CIRCUITD are needed to add negative numbers

Question 21

What’s in jk nit in sr ( 3 things and state their advantages)

Answer 21

-Jk is master slave with clock , which means clock must switch from los to high for input of master to affect output of slave
- a clock common to both master and slave avoids the propagation of delays

• s=r=1 is forbidden now, and j=k=1 is a toggle
• also preset and clear bar allows for output to be changed irrespective of inputs, being active low

Question 22

Why better to have more gates

Answer 22

• breaks down circuit into smaller manageable chunks to test and debug
• can add more functions

Question 23

So does Tristan’s allow microprocessor to read and write data i

Answer 23

If Trista tell on or off due to if chip select / read or write on or off, it will either activate the date out or data in

Question 24

Explain difference between file register instructions and literal instructions

Answer 24

Literal = instructions operate on constant data embodied directly within thr isntruction itself

FILE REGISTER instructions = operating e on data located in the file register of the pic microprocessor memory, their argument is in the address of the file register where the data is stored

Question 25

When is there dc

Answer 25

When 1+1 occurs in 3rd bit

Question 26

What is standard DAC and it’s drawback

Answer 26

KPa p ideal so temrknak virtual
Voltages at each point contribute currents that make up final voltages
- not ideal because resistors different values different materials TEMPERTAURE variation
Accuracy is crazy
Needs a lot of resistors

Question 27

How to do day voltsge

Answer 27

Whatever number they give that’s the max voltsge

Find currents and multiply

Check the rail of opamp, it will, be that sign

Question 28

How to do max range q for memory chip

Answer 28

3 lines means 4 bits at the front to give 8 locations
Start that from 0 to 7 to give 8
Then for each chip the min is 0 for the rest and 1 for all
Then represent in he’s