Electricity: Class 10 Science Q&A · Page 9
281 free answers on Electricity (Science) for Class 10 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- ScienceClass 10ICSE
Give two examples of substances which are good conductors of electricity. Why do you think they are good conductors of electricity? b) Calculate the resistance of a copper wire 1.0km long and 0.50mm diameter if the resistivity of copper is 1.7×10-8Ωm.
Two examples of substances that are good conductors of electricity are silver and These two metals have free electrons that are available for conduction. Given, l = 1km = 1000m r = d/2 = 0.5/2mm = 0.25mm = 0.25×10-3m ρ = 1.7×10-8Ωm We know that, R = ρl/A R = 86.6Ω
- ScienceClass 10ICSE
Write down an expression for the resistance of a metallic wire in terms of the resistivity. b) What will be the resistance of a metal wire of length 2 metres and area of cross-section 1.55×10-6m2, if the resistivity of the metal be 2.8×10-8Ωm?
Following is the expression for the resistance of a metallic wire in terms of the resistivity: R = ρl/A Where, R is the resistance of the wire ρ is the resistivity of the wire A is the cross-sectional area of the wire l is the length of the wire Given, l = 2m A = 1.55×10-6m2 ρ = 2.8×10-8Ωm We know that, R = ρl/A = 0.036 ohm
- ScienceClass 10ICSE
What do you understand by the “resistivity” of a substance? b) A wire is 1.0m long, 0.2 mm in a diameter and the has a resistance of 10Ω. Calculate the resistivity of its material?
Resistivity is defined as the characteristic property of a substance which is dependent on the nature of the substance and the temperature of the substance used in the It is numerically equal to the resistance between the opposite faces of a cube with sides 1m. Given, l = 1m r = d/2 = 0.2/2 = 0.1mm = 0.0001m R = 10ohm We know that, R = ρl/A ρ = RA/l = 31.4×10-8ohm
- ScienceClass 10ICSE
Fill in the following blanks with suitable words: Resistance is measured in ………… the resistance of a wire increases as the length as the temperature ……… and as the cross-sectional area …….. Answer:
Ohm, increases, increases, and decreases.
- ScienceClass 10ICSE
How does the resistance of a pure metal change if its temperature decreases? b) Hoes does the presence of impurities in a metal affect its resistance?
As the temperature decreases, the resistance of the material also Presence of impurities in a metal increases the resistance of the
- ScienceClass 10ICSE
Which has more resistance: a) A long piece of nichrome wire or a short one? b) A thick piece of nichrome wire or a thin piece? Answer:
Following has more resistance: A long piece of nichrome wire A thin piece of nichrome wire
- ScienceClass 10ICSE
Why are the coils of electric iron and electric toasters made of an alloy rather than a pure metal?
The coils of an electric iron and electric toasters are made of an alloy rather than a pure metal because: The resistivity of an alloy is higher when compared to the pure metal Alloys don’t undergo oxidation at high temperatures
- ScienceClass 10ICSE
Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.
Following are the two reasons why nichrome alloy is used for making the heating elements of electrical appliances: The resistivity of nichrome is very Nichrome doesn’t undergo oxidation at high
- ScienceClass 10ICSE
What is nichrome? State its one use
Nichrome is a alloy material obtained from nickel, chromium, manganese, and iron. The resistivity of nichrome is 60 times more than that of copper. It is used in making of the elements that are used for heating in most of the electrical heating appliances.
- ScienceClass 10ICSE
Name the material which is used for making the heating element of an electric iron.
Nichrome is the material which is used for making the heating element of an electric iron.
- ScienceClass 10ICSE
Why are copper and aluminum wires usually used for electricity transmission?
Copper and aluminum wires are used for electricity transmission because they have low resistivities.
- ScienceClass 10ICSE
Which among iron and mercury is a better conductor of electricity?
Among iron and mercury, iron is a better conductor of electricity. The resistance of iron is less than mercury and we know that resistance is inversely proportional to the current. Therefore, iron is better as a conductor of electricity when compared to the mercury.
- ScienceClass 10ICSE
Name the material which is the best conductor of electricity.
Silver metal is the best conductor of electricity. This is because the electrons of silver metal are available for free movement when compared to the other metals.
- ScienceClass 10ICSE
If the length of a wire is doubled by taking more of wire, what happens to its resistance?
The resistance of the wire becomes double when the length of the wire is doubled. This is because length is directly proportional to the resistance while area of cross section is inversely proportional to the resistance. Also, we know that R = (ρl)/(A) Therefore, if l becomes double, then R becomes 2R.
- ScienceClass 10ICSE
What happens to the resistance as the conductor is made thicker?
As the thickness of the conductor is increased, the resistance of the conductor decreases. This is because: R = (ρl)/(A) Where, R is the resistance l is the length of the conductor A is the area of cross section of the conductor And ρ is the resistivity Since, area is directly proportional to the radius of the wire, increase in cross-sectional area or the thickness will result in decrease in resistance and current flow will be more.
- ScienceClass 10ICSE
A current of 200mA flows through a 4kΩ resistor. What is the potential difference across the resistor?
Given, Current, I = 200mA = 0.2A Resistance, R = 4kΩ = 4 × 103 Ohm = 4000 Ohm We know that, V = IR V = 0.2 × 4000 V = 800 volt
- ScienceClass 10ICSE
A potential difference of 10V is needed to make a current of 0.02A flow through a wire. What potential difference is needed to make a current of 250mA flow through the same wire?
First case, Given, Current, I = 0.02A Voltage, V = 10 volt We know that, V = IR 10 = 0.02 × R R = 10/0.02 = 500 Ohms Second case, Current, I = 250 × 10-3 A Resistance, R = 500 Ohm V = IR V = 250 × 10-3 × 500 = 125 volt
- ScienceClass 10ICSE
The graph between V an d I for a conductor is a straight line passing through the origin. a) Which law is illustrated by such a graph? What should remain constant in a statement of this law?
Ohm’s law is illustrated by the V-I graph in which the straight line is passing through the For Ohm’s law to hold good in the given situation, temperature must remain
- ScienceClass 10ICSE
Name the electrical property of a material whose symbol is “omega”.
The electrical property resistance of the material has the symbol “omega”.
- ScienceClass 10ICSE
An electric room heater draws a current of 2.4A from the 120V supply line. What current will this room heater draw when connected to 240V supply line?
Answer: First case: Given, Current, I = 2.4amp Voltage, V = 120V We know that, V = IR 120 = 2.4 × R R = 120/2.4 = 50 Ohm Second case: Given, Voltage, V = 240 volt Resistance, r = 50 Ohm We know that, V = IR 240 = I × 50 I = 4.8 amp