K.C.S.E Physics Q & A - MODEL 2012PP2QN015

K.C.S.E Physics Q & A - MODEL 2012PP2QN015

​Figure 14, shows a circuit in which a battery, a switch, a bulb, a resistor P, a variable resistor Q, a voltmeter V and two ammeters A1 and A2 of negligible resistance are connected.

​P has a resistance of 10Ç2. When the switch is closed A1 reads 0.1OA and the voltmeter reads 1.5V.
(a) Determine;
(i) the current passing through P. 
(ii) the resistance of the bulb. 
(b) The variable resistor  is now adjusted so that a larger current flows through A2.
(i) State how this will affect the resistance of the bulb. 
(ii) Explain your answer in b(i). 
(c) A house has one 100W bulb, two 60W bulbs and one 30W bulb. Determine the cost of having all the bulbs switched on for 70 hours, given that the cost of electricity is 40 cents per kilo-watt hour. 

answers

​(b) (i) the resistance of the bulb would increase;
(ii) Current is higher hence increases; temperature increased temperature results in increased resistance;