MCQ
Which among the following is not attracted by magnets?
- AIron
- BCobalt
- CCopper
- DNickel
Explanation:
A magnet is a material that has both attractive and directive properties. It attracts small pieces of iron, nickel, cobalt, etc. This property of attraction is called magnetism. Going by this criteria, copper is not attracted by magnets.
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Why are red coloured lights are used in traffic signals to stop the vehicles?
The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use
|
(a) 400 Ω |
(b) 200 Ω |
(c) 40 Ω |
(d) 20 Ω |
1 mg gold undergoes decay with 2.7 days half-life period, amount left after 8.1 days is
|
(a) 0.91 mg |
(b) 0.25 mg |
(c) 0.5 mg |
(d) 0.125 mg |
The forbidden gap in the energy bands of germanium at room temperature is about
|
(a) 1.1 eV |
(b) 0.1 eV |
(c) 0.67 eV |
(d) 6.7 eV |
A glass slab of thickness 3 cm and refractive index 3/2 is placed on ink mark on a piece of paper. For a person looking at the mark at a distance 5.0 cm above it, the distance of the mark will appear to be
|
(a) 3.0 cm |
(b) 4.0 cm |
(c) 4.5 cm |
(d) 5.0 cm |
If critical angle for a material to air is 30o, the refractive index of the material will be
|
(a) 1.0 |
(b) 1.5 |
(c) 2.0 |
(d) 2.5 |