Question

How will you connect three resistors of 3 Ohm, 4 Ohm and 7 Ohm respectively so as to obtain a resultant resistance of 3.5 Ohm?

• A. 3, 4, 7 in series
• B. 3, 4, 7 in parallel
• C. 3,4 in series and then parallel with 7
• D. 3,4 in parallel and then series with 7

Answer 1

Answer: (C)

. 3,4 in series and then parallel with 7

When 3 Ohm, 4 Ohm are in series we get total resistance = 3 + 4 = 7 Ohm.

When two 7 Ohm resistance are in parallel we get 3.5 Ohm as total resistance as follows

$\frac{1}{R}$ = $\frac{1}{7}$ + $\frac{1}{7}=\frac{2}{7}$

$R=\frac{7}{2}=3.5$ Ohm.