Class X Sciences
[papers from previous years]

Two resistors, with resistances 5 Ωand
15 Ω are to be connected to a battery of emf
9 V so as to obtain:

(i) minimum current
(ii) maximum current

(a) Show with the help of a diagram how you would connect the
resistances in each case.
(b) Calculate the strength of the total current in the circuit
in each of the two cases.

1

Answers

2015-05-01T12:28:06+05:30
(i) for minimum current join the both resistance in series.

(ii) for 
maximum current join both resistors in parallel 

(a) see the attachment

(b) 
for minimum:-
resistance are join in series so total resistance is
 R = 5 + 15   = 20 Ω
from ohm's low current
I = V  =  9  = 0.45 A     
     R     20 

for maximum:- 
resistance are join in parallel so total resistance is
 1 = 1  +  1
 R    5    15 
    = 3 +1  Ω   
        15 
 1   = 4  
Ω  
 R    15

for R = 
15  Ω
            4
from ohm's low current
I = V   9 x 4  = 2.4 A     
     R        15
0