+91-8076753736[email protected]
logo
logo
-->

Current Electricity

Question
CBSEENPH12037937
Wired Faculty App

A battery of emf E and internal resistance r gives a current of 0.5 A with an external resistor of 12 Ω, and a current of 0. 25 A with an external resistor of 25 Ω. Calculate (a) internal resistance and (b) emf of battery.

Solution
A battery of emf E and internal resistance 'r' gives us a current of 0.5 A with an external resistance 12Ω and also a current of 0.25 A with an external resistor of 25 Ω .
Using the formula,  I = ER+r 

i.e.,                    0.5= E12+r  and,  0.25 = E25+r

(a) On dividing the above equations we get,
            
                     0.50.25 = 25+r12+r
                     
                 ⇒ 2 = 25+r12+r       r = 1 Ω 

which is the required resistance.

(b) Putting the value of 'r' in the above formula we will find the 'emf' of the battery. 

                     0.5 = E12+1  ⇒  E = 6.5 V
 

Some More Questions From Current Electricity Chapter

What conclusion can you draw from the following observations on a resistor made of alloy manganin?

Current A

Voltage V

Current A

Voltage V

0.2

0.4

0.6

0.8

1.0

2.0

3.94

7.87

11.8

15.7

19.7

39.4

3.0

4.0

5.0

6.0

7.0

8.0

59.2

78.8

98.6

118.5

138.2

158.0

Mock Test Series

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation