(a) List the factors on which the resistance of a conductor in the shape of a wire depends. (b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason. (c) Why are alloys commonly used in electrical heating devices? Give reason.
(a) List the factors on which the resistance of a conductor in the shape of a wire depends. (b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason. (c) Why are alloys commonly used in electrical heating devices? Give reason.
(a) The resistance of a conductor in the shape of a wire depends on the following factors:
- Length of the wire: Resistance is directly proportional to the length of the wire.
- Cross-sectional area of the wire: Resistance is inversely proportional to the cross-sectional area of the wire.
- Material of the wire: Different materials have different resistivities.
- Temperature of the wire: Resistance is affected by the temperature of the wire.
(b) Metals are good conductors of electricity because they have free electrons that can move freely within the metal lattice, allowing the flow of electric current. On the other hand, glass is a bad conductor of electricity because it has a rigid and regular structure, with no free electrons to carry electric current.
(c) Alloys are commonly used in electrical heating devices because they have high resistivity, which allows them to produce heat when an electric current flows through them. Additionally, alloys have a high melting point, which makes them suitable for use in high-temperature applications.
Marking Scheme
- 13 marks
Quick Oral Answer
The resistance of a conductor depends on its length, cross-sectional area, material, and temperature. Metals are good conductors because they have free electrons, while glass is a bad conductor due to its rigid structure. Alloys are used in heating devices because of their high resistivity and melting point.
Analysis & Explanation
This question requires the student to analyze the factors affecting resistance, explain why metals are good conductors and glass is a bad conductor, and justify the use of alloys in electrical heating devices. The student needs to apply their knowledge of electricity and materials to answer this question.
Common Mistakes
- 1Forgetting to mention the factors affecting resistance
- 2Not explaining why metals are good conductors and glass is a bad conductor
- 3Not justifying the use of alloys in electrical heating devices
Interesting Facts
The resistivity of a material can vary greatly depending on its temperature.
Some alloys have a negative temperature coefficient of resistance, meaning their resistance decreases with increasing temperature.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2018?
This question carries 3 marks in the CBSE Class 10 Science 2018 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Electricity" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Electricity" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2018 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2018 paper.