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Current Electricity

Question
CBSEENPH12047769
Wired Faculty App

For a metallic wire, the ratio Vi ( V = applied potential difference and i = current flowing) is

  • independent of temperature

  • increases as the temperature rises

  • decreases as the temperature rises

  • increases or decreases as temperature rises depending upon the metal 

Solution

B.

increases as the temperature rises

The resistance of a metallic wire at temperature t°C is given by 

Rt = Ro ( 1 + α t )

Where α is coefficient of expansion.
Hence, resistance of wire increases on increasing the temperature. Also, from Ohm's law, Viratio is equal to R ie

Vi = R

Hence, on increasing the temperature the ratio Vi increases.

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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