Can someone solve these?

Question

Answer 1

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a and b are the same with different values. c requires a Y to delta transformation

b) 300 and 150 in series = 450

60 and 90 in series = 150

now you have 450 and 150 in parallel which is

450•150/600 = 112.5 Ω

that is in series with 20 for a total R of 132.5 Ω

battery current = 8/132.5 = 0.0604 amps

voltage across the parallel pair = .0604 x 112.5  = 6.79 volts

that causes current in both the 300 and 150 of

6.79 / 450 = 0.0151 amps

and it causes current in both the 90 and 90 of6.79 / 150 = 0.0453 amps

and they add up to 0.0604 amps as a check

power in the 150 = I²R = 0.0151²150 = 0.0342 watts

the second I'll leave to another answer.

hint: apply a Y to delta transformation to the 4,5,6 Ω resistors, then you have simple parallel series combos.

Answer 2

how about reading your electrical chart and work it out yourself , its under ohms law , basic eletrical formula ..

Answer 3

Assume i1, i2 an i3 clockwise currents in the left, bottom and top loops. Currents I1, I2, I3, I4 and I5 will be found using those.

The equations are:

-5i1 + 3i2 + 2i3 = -6.6

+3i1 -  12i2 + 5i3 = 0

+2i1 + 5i2 - 13i3 = 0

With the equations you can use any method for simultaneous solutions. 

Multiply 3rd eq. by -1.5 and add to 2nd eq,

-39i2 + 49i3 = 0 so i3 = 39i2/49

Multiply the 2nd eq by 5/3 and add to 1st eq.

-17i2 + 31i3/3 = -6.6

i3 = 51i2/31 - 19.8/31 = 39i2/49

i2(51/31 - 39/49) = 19.8/31

i2 = 0.7521

i3 = 0.5986

i1= (3*0.7521+2*0.5986+6.6)/5 = 2.01

I1 = 2.01 - 0.7521 = 1.259

I2 = 0.7521

I3 = i2 - i3 = 0.1535  

I4 = I3 + I1 = 1.412

I5 = 2.01 - 1.412 = 0.599

 

Answer 4

fig. (a)

Req = (16 // 6) + 3 = 96/22 + 3 = 162/22 = 81/11 ohm

I = V/Req = 20*11/81 =  220/81 = 2.716 A 

fig. (b)

Req = (150 // 450) + 20 = 50*(27/12) + 20 = (1350+240)/12 = 1590/12 ohm

I = V/Req = 8*12/1590 = 96/1590  A 

I(300) = I*150/600 = 24/1590 A 

I(90) = I*450/600 = 72/1590 A

P(150) = 150*24^2/1590^2 =  34.2 mwatt

 

Answer 5

electric resistance / current problems - - - this is PHYSICS