HOW DO I GET TOTAL RESISTANCE ON PARALLEL

Question

i used this formula, Rt=1/1/R1 1/R2 1/R3 1/R4. RESISTOR1 OR R1 IS 20 OHMS, R2 IS 10, R3 IS 50 AND R4 IS 1OO. THIS RESISTORS ARE IN PARALLEL. DO I HAVE TO FIND THE LCD?(LESS COMMON DENAMINATOR)

Answer 1

I thought you added them when they were in series. In parallel isn't it just the largest one - 100. I could be very wrong about this.

Answer 2

Parallel is 1/(1/R1+ 1/R2+1/R3+...) in your case 1/(1/20+1/10+1/50+1/100) which changes to 1/(10/100+5/100+2/100+1/100) which then changes to 1/(18/100) = 100/18 which equals 5.55 ohms.

EDIT:

Nil that formula only works with 2 resistors at a time. You can do R1*R2/R1+R2=Req1 then Req1*R3/Req1+R3=Req2 then Req2*R4/Req2+R4.

EDIT2:

And no Blue when they are in parallel the resistors are actually closer to the smaller value. When they are in series they are closer to the larger value. In series they are equal to 180ohms in parallel they are equal to 5.55ohms

Answer 3

Ill show u a little trick.

normally all u do is add them up and reciprocate it as the previous answer said

theres quite another easier way

say r1 r2 and r3 are resistors in parallel

then rt=(r1*r2*r3)/(r1+r2+r3)

this is- multiply the resistors and divide by the sum!try it for any number of resistors!

its just faster and u get to knw this later on in uni!

happy resisting!