Question

What is the resistance between A and B in the figure given?
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Answer 1

Answer:

Given :-

• Three resistors connected in series with each other and connected in parallel to 30 ohm resistor.
• This connection is then connected with other 2 resistors in series.
• There a total of 6 resistors in the connection between the two points that I A and B.

Now, we name the resistors for convenience in calculating the resistance. For the naming, refer the diagram attached.

Process of referring such questions –

1. Here, firstly we need to calculate the net resistance in series connections for resistors (a), (b) and (c).
2. Then, with tge resistance we got, we need to find the net resistance for the parallel connection with (d).
3. After that, we need to find the net resistance between the points A and B in series connection with the help of (e) and (f).

Solution –

R(series) = R1 + R2 + R3 .... Rn

Rs = R(a) + R(b) + R(c)

Rs = 10 + 20 + 20

Rs = 50 ohm

Now, 1/R(parallel) = 1/R1 + 1/R2 .... 1/Rn

1/Rp = 1/Rs + 1/R(d)

1/Rp = 1/50 + 1/30

1/Rp = (30 + 50)/1500

1/Rp = 80/1500 = 8/150

Rp = 150/8

Rp = 18.75 ohm

Finally, R(series) = R1 + R2 + R3 .... Rn

Rs = R(e) + R(f) + R(parallel)

Rs = 10 + 10 + 18.75

Rs = 20 + 18.75

Rs = 38.75 ohm