circuits midterm 1 review

1c equal to how many electrons?

6.24×10^-19 electrons

1e equal to how many coloumbs?

1.6×10^-19 C

charge over t graph (q vs t) what is the integral of this?

integral is total charge

charge over time graph (q vs t) what is the slope of it?

slope= i (current)

what is the formula for energy?

W = pt (power x time)

what is the formula for Q charge?

Q = n(±e)

what is the derivative of Q / q

i = dq/dt (derivative of q is the current)

current density

Current density (j):

i= e⋅n⋅v⋅S

• n: carrier concentration

• v: drift velocity

• S: cross-sectional area

voltage

Voltage = Potential Difference:

V = Energy / Charge

V = W / q

what happens to power if enter negative terminal first

Power is negative —> deliver

what happens if the power enters the positive terminal first?

Power is positive

Power is absorbed

resistance of wire

Resistance of a wire:

R=ρ⋅L / A

where ρ\rhoρ is resistivity, LLL is length, and AAA is cross-sectional area.

conductance formula

G = 1/R

voltage divider

voltage in series.

V₃= R 3 / (R1+R2+R3) (V)

current division

current in parallel.

i1 = R2 / R1+R2 i

numerator opposite of what you are looking for

power formulas

P = IV = I2R = V²/R

supermesh

u can use supermesh when u have a current source in the middle of two branches

this is when u can remove the middle branch and do mesh analysis around the whole thing

linearity property

K v = K i r

superposition steps

1. turn off all independent sources except 1

2. solve

3. then do it again for all

4. sum them up

thevenin’s steps

No independent sources

1. turn off indepndent sources

2. find Rth = Req

3. turn on sources

4. find Vth\

   (If there is a resistor connected vertical then u remove it)

thevenin steps

WITH DEPENDENT SOURCES

1. turn off independent

2. add 1 v to AB terminal

3. find current

4. then u can find Rth

5. turn back on independent source —> find current —> VTh with Rth

Norton’s step

NO DEPENDENT SOURCES

1. turn off independent

2. find Req = Rn = Rth

3. turn on sources

4. Find I_sc=I_n

Norton’s Steps

WITH DEPENDENT SOURCES

1. turn off independent sources

2. apply 1 v or 1 a between AB

3. find Rn = V_ab/i_ab

4. turn on all sources

5. find I_sc = In

relationship between thevenin and norton

Vth = I_nR_th

op amps

i1 = i2

v1 = v2 = v_s