Advertisements
Advertisements
प्रश्न
What is meant by the "resistance of a conductor" ? Write the relation between resistance, potential difference and current.
Advertisements
उत्तर
Resistance is the property of a conductor to resist the flow of charge through it. The relation between resistance, current and potential difference is V = IR.
APPEARS IN
संबंधित प्रश्न
What is (a) the highest, (b) the lowest total resistance that can be secured by combinations of four coils of resistance 4 Ω, 8 Ω, 12 Ω, 24 Ω?
A copper wire has diameter 0.5 mm and resistivity of 1.6 × 10−8Ω m. What will be the length of this wire to make its resistance 10 Ω? How much does the resistance change if the diameter is doubled?
List the factors on which the resistance of a conductor in the shape of a wire depends.
Why are alloys commonly used in electrical heating devices? Give reason.
Classify the following into good conductors, resistors and insulators:
Rubber, Mercury, Nichrome, Polythene, Aluminium, Wood, Manganin, Bakelite, Iron, Paper, Thermocol, Metal coin
Which has more resistance:
a thick piece of nichrome wire or a thin piece?
What do you understand by the "resistivity" of a substance?
Give two examples of substances which are good conductors of electricity. Why do you think they are good conductors of electricity?
How does the resistance of a conductor depend on:
area of cross-section of the conductor?
How does the resistance of a conductor depend on:
temperature of the conductor?
What would be the effect on the resistance of a metal wire of:
increasing its length?
The figure blow shows a variable resistor in a dimmer switch.
How would you turn the switch to make the lights: (a) brighter, and (b) dimmer? Explain your answer.
Write the relation between resistance and electrical resistivity of the material of a conductor in the shape of a cylinder of length `'l'` and area of cross-section `'A'` . Hence derive the S.I. unit of electrical resistivity.
The element used almost exclusively for filaments of incandescent lamps:
A cylindrical conductor of length l and uniform area of cross-section A has resistance R. Another conductor of length 2l and resistance R of the same material has an area of cross-section:
Use the data in the Table given below to answer the following –
Which material is the best conductor?
Table give below Electrical resistivity of some substances at 20°C
| Electrical resistivity of some substances at 20°C | ||
| − | Material | Resistivity (Ω m) |
| Conductors |
Silver | 1.60 × 10−8 |
| Copper | 1.62 × 10−8 | |
| Aluminium | 2.63 × 10−8 | |
| Tungsten | 5.20 × 10−8 | |
| Nickel | 6.84 × 10−8 | |
| Iron | 10.0 × 10−8 | |
| Chromium | 12.9 × 10−8 | |
| Mercury | 94.0 × 10−8 | |
| Manganese | 1.84 × 10−6 | |
| Alloys |
Constantan (alloy of Cu and Ni) |
49 × 10−6 |
| Manganin (alloy of Cu, Mn and Ni) |
44 × 10−6 | |
| Nichrome (alloy of Ni, Cr, Mn and Fe) |
100 × 10−6 | |
| Insulators | Glass | 1010 − 1014 |
| Hard rubber | 1013 − 1016 | |
| Ebonite | 1015 − 1017 | |
| Diamond | 1012 − 1013 | |
| Paper (dry) | 1012 | |
How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?
Plastic insulation surrounds a wire having diameter d and length l as shown above. A decrease in the resistance of the wire would be produced by an increase in the ______.
How will the resistance of a wire be affected if its
- length is doubled, and
- radius is also doubled ?
Give justification for your answer.
