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Current Electricity

Question

Wired Faculty App

When a resistor of 20 Ω is connected in series with a battery, the current is 0.5 A. When a resistor of 10 Ω is connected, the current becomes 0.8 A. Calculate the emf and the internal resistance of the battery.

Solution

Let, 'E' be the emf of the battery and 'r' its internal resistance.
Using the relation,

E = I [R + r]

Given,

E = 0.5 (20 + r)

...(1)

E = 0.8 (10 + r)

...(2)

i.e.,

0.5 (20 + r) = 0.8 (10 + r)

\Rightarrow

10 + 0.5 r = 8 + 0.8 r

\Rightarrow

0.3 r = 2, r = 6.67 Ω

Therefore,

E = 0.5 \times 26.67 = 13.34 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

Answer the following questions:
A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?

Answer the following questions:
Is Ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law.

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