Physics - Mr. Sreekumaran Nair
1. They have high resistively and low temperature coefficient of resistance.
2. 22*102 Ω ± 10%
3. Resistively remains the same.
4. As Vd α V. The different velocity will be doubled.
5. R=ρ(l/A)
= ρ(l2/Al)
= ρl2/V)
since, ρ and V are constants
therefore, R α l2
(R2/R1) = (l2/l1)2=9
because R2=9R1
=9*10=90 Ω
6. Now, 1/R=1/R1+1/R2 because l = 48/240 = 0.2 m
7. a) in parallel, power dissipation α 1/R
Therefore 3Ω wire will dissipate more power
b) In series , power dissipation α R
Therefore 9Ω wire will dissipate more power
8. R100/R27.5 = (1+100α)/(1+27.5α)
On solving, we get
α = 0.0039/˚c
9. Superconductors are the materials that lose all its resistance at very low temperature
=0 K
Application:
Super conductor are used
a) In making very strong electromagnets
b) In producing very high speed computers .
10. Resistivity of copper is less , hence manganin wire is thicker.
11. High value of resistivity and low value of temperature coefficient.
12. Resistivity will be unchanged because it depends upon nature of the materials.
13. B is more sensitive.
14. Reduced by half.
15. Relaxation time decreases with increase of temperature.
16. Increase in heat.
17. Reistance remains same.
18. Pα 1/R. (i.e) 25Watts
19. 16 times of the original reisitance.
20. (i)Series - Iron
(ii)Parallel - Copper.
21. R = r L/A.
(i.e) 10.25%
22. Parallel(i.e) R.
23. 1:4.
24. 2:1
25. R.
CBSE Physics (Chapter Wise With Hint / Solution) Class XII (By Mr. Sreekumaran Nair)