1)How long will it take to fill a water tank of 400 litres capacity kept over
a roof when the rate of flow water to the tank is 0.222 litres per

2)An electric bulb is switched on for 5 hours. If its filament draws 0.5
ampere current, calculate the amount of electric charge that has
passed through the filament.

3)The electrical resistivities of five substances A, B, C, D and E are given
A. 5.20 x 10-8
B. 110 x 10-8
C. 2.60 x 10-8
D. 10.0 x 10-8
E. 1.70 x 10-8
a. Which substance is the best conductor of electricity?
b. Which one is a better conductor: A or C? Why?
c. Which substance would you advice to be used for making
heating elements of electric iron? Why?
d. Which two substances should be used for making electric wires?



(i) 30min or ½hour., (ii)q=it, q=0.5×(5×60×60) , q=9×10³c, (iii)(a)E1.70×10-8, (b)C,because it has low resistance (c)