Advertisements
Advertisements
प्रश्न
Two wires of equal length, one of copper and the other of manganin have the same resistance. Which wire is thicker?
Advertisements
उत्तर
Since the resistivity of alloy is greater than the resistivity of its constituents. We have resistivity of manganin greater than resistivity of copper metal.
So, Resistance `R = ρ1/A`
Where l is length and A is area of cross-section of material.
Also ρ is the resistivity of the material.
For copper, `R_c = ρ_c l_c/A_c`
and for magnanin `R_m = ρ_m l_m/A_m`
We have
`ρ_m>ρ_c`
`or ρ_m/ρ_c > 1`
`As l_c = l_m`
Dividing `R_c/R_m = (ρ_cA_m)/(ρ_mA_c)`
Again `R_c = R_m`
`therefore ρ_c A_m = ρ_mA_c`
`ρ_m/ρ_c=A_m/A_c >1`
Hence `A_m >A_c`
Or, Manganin wire is thicker.
संबंधित प्रश्न
A negligibly small current is passed through a wire of length 15 m and uniform cross-section 6.0 × 10−7 m2, and its resistance is measured to be 5.0 Ω. What is the resistivity of the material at the temperature of the experiment?
Two wires of equal length, one of aluminium and the other of copper have the same resistance. Which of the two wires is lighter? Hence explain why aluminium wires are preferred for overhead power cables.
(ρAl = 2.63 × 10−8 Ω m, ρCu = 1.72 × 10−8 Ω m, Relative density of Al = 2.7, of Cu = 8.9.)
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 | 3.94 | 3.0 | 59.2 |
| 0.4 | 7.87 | 4.0 | 78.8 |
| 0.6 | 11.8 | 5.0 | 98.6 |
| 0.8 | 15.7 | 6.0 | 118.5 |
| 1.0 | 19.7 | 7.0 | 138.2 |
| 2.0 | 39.4 | 8.0 | 158.0 |
A heating element is marked 210 V, 630 W. Find the resistance of the element when connected to a 210 V dc source.
A wire of length 1 m and radius 0.1 mm has a resistance of 100 Ω. Find the resistivity of the material.
What length of a copper wire of cross-sectional area 0.01 mm2 will be needed to prepare a resistance of 1 kΩ? Resistivity of copper = 1.7 × 10–8 Ωm
If R1 and R2 are filament resistances of a 200 W and a 100 W bulb respectively, designed to operate on the same voltage, then:
The resistivity of alloy manganin is ______.
If the last band on the carbon resistor is absent, then the tolerance is ______
