If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance?

The electrical resistivities of five substances A, B, C, D and E are given below :

A) 5.20 x 10^-8 Ω m

B) 2.60 x 10^-8 Ω m

C) 10.0 x 10^-8 Ω m

D) 1.70 x 10^-8 Ω m

(a) Which substance is the best conductor of electricity? Why?

(b) Which one is better conductor: A or C? Why?

(c) Which substance would you advice to be used for making heating elements of electric irons? Why?

(d) Which two substances should be used for making electric wires? Why?

Give the law of combination of resistances in series.

State the law of combination of resistances in parallel.

If 3 resistances of 3 ohm each are connected in parallel, what will be their total resistance?