Question

(a) What is meant by the 'series combination' and 'parallel combination' of resistors? Explain with diagrams.
(b) What is the combined resistance of the three resistors of 5 Ω, 3 Ω and 2 Ω connected as shown in the figure?

Answer 1

(a) In a series combination, the resistances are connected with end to end in contact, such that current flow is equal in all the resistances in the combination. Whereas in the parallel combination, resistances are connected in such a manner that they get an equal voltage across their ends.



(b) 3-ohm and 2-ohm resistors are connected in series, and their combination is connected in parallel with the 5-ohm resistor.

Net resistance of the series combination of 3-ohm and 2-ohm resistance = $3\mathrm{\Omega }+2\mathrm{\Omega }=5\mathrm{\Omega }$

This 5-ohm resistance is in parallel combination with given 5-ohm resistance.

Hence, the total equivalent resistance of the given combination = $\frac{5\mathrm{\Omega }\times 5\mathrm{\Omega }}{5\mathrm{\Omega }+5\mathrm{\Omega }}=2.5\mathrm{\Omega }$