Chapter 12: Electricity- Exercise- 3

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Chapter 12: Electricity

Class: X

Exercise 3

 

Question 1

On what factors does the resistance of a conductor depend?

Answer 1

The resistance of a conductor depends upon the following factors:

• Length
• Thickness or Cross-sectional area
• Conductivity
• Temperature

Question 2

Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?

Answer 2

Resistance (R) of the wire is inversely proportional to the area of cross-section (A).

It means thick wire will have less resistance as compared to a thin wire. Therefore, current will flow more easily through a thick wire than a thin wire.

Question 3

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

Answer 3

According to the Ohm’s law, V = IR

If the resistance remains constant, V is directly proportional to I.  i.e,

Therefore, if potential difference is reduced to half of its original value, the current will become half of its original value.

Question 4

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

Answer 4

The resistivity of an alloy is higher than the pure metal and it does not corrode easily. Moreover, even at high temperatures, the alloys do not melt readily. Hence, the coils of heating appliances such as electric toasters and electric irons are made of an alloy rather than a pure metal.

Question 5

Use the data in Table 12.2 to answer the following:

1. Which among iron and mercury is a better conductor?
2. Which material is the best conductor?

 

 

Answer 5:

10. Iron is good conductor as compared to mercury because resistivity of iron (10.0 × 10–8 Ω m) is lesser than that of the mercury (94.0 × 10–8 Ω m).

1. Silver is the best conductor because it has the lowest resistivity.