K.C.S.E Physics Q & A - MODEL 2010PP2QN17

K.C.S.E Physics Q & A - MODEL 2010PP2QN17

​(a) Figure 12, shows an electrical circuit including three switches, S1, S2, S3, and three identical lamps L1, L2, L3. A constant potential difference is applied across X and Y.

​(î) Other than L1, state the lamp that will light when S1 and S2 are closed. 
(ii) How does the brightness of L1 in (i) above compare with its brightness when all the switches are closed? 
(iii) Explain the observation in part (ii) above.
(b) Figure 13, shows a cell in series with a 3ohms resistor and a switch. A high resistance voltmeter is connected across the cell.

The voltmeter reads 1.5V with the switch open and 1.2V with the switch closed.
(i) State the electromotive force of the cell. 
(ii) Determine the current through the 3ohms resistor when the switch is closed. 
(iii) Determine the internal resistance of the cell. 
(c) (î) Another resistor R is connected in series with the 3ohms resistor so that a current of 0.15A flows when the switch is closed. Determine the resistance of R. 

answers