Question

Harry went to the electronic shop to buy a 17.5 ohm resistor for his project. However, the store only has 5 ohm resistor. What is the minimum number of 5 ohm resistors must he buy? How will he connect these resistors to come up with 17.5 ohm resistance, he is expected to use all the resistors that he will buy.

Answer 1

$17.5+5\cdot3=2.5 \ (\Omega)$

$n_1=3$

$2.5=1/(n_2/5)\to n_2=2$

$n=n_1+n_2=3+2=5$ . Answer

Three resistors must be connected in series and two in parallel.

$5+5+5+(\frac{1}{1/5+1/5})=17.5\ (\Omega)$