Current Electricity and Electrical InstrumentMedium
Question
The efficiency of a cell when connected to a resistance R is 60%. What will be its efficiency if the external resistance is increased to six times.
Options
A.80 %
B.90 %
C.55 %
D.95 %
Solution
η = 
= 1 − 
= 0.6 ⇒ R = 0.6 r + 0.6 R
r =
R = 
⇒ η = 
= 0.9 = 90%
= 1 − = 0.6 ⇒ R = 0.6 r + 0.6 Rr =
R = ⇒ η = = 0.9 = 90% Create a free account to view solution
View Solution FreeTopic: Current Electricity and Electrical Instrument·Practice all Current Electricity and Electrical Instrument questions
More Current Electricity and Electrical Instrument Questions
Consider a thin square sheet of side L and thickness t,made of a material of resistivity ρ. The resistance between ...The current in the given circuit is :...There is a current of 40 ampere in a wire of 10-6 m2 area of cross-section. If the number of free electron per m3 is 102...An insulating pipe of cross - section area ′A′ contains an electrolyte which has two types of ions: their ch...A conducting square frame of side ′a′ and a long straight wire carrying current I are located in the same pl...