- ADiscontinuity.
- BPoor conductivity.
- CNeedle end.
- DLow melting point.
Explanation:
Needle end can arrest the lightning easily. Besides, the device must provide a continuous path to electricity so that current passes to ground. It must have a high melting point else it will meltdown due to the heat generated during carrying lightning current.
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Assertion : On going away from a point charge or a small electric dipole, electric field decreases at the same rate in both the cases.
Reason : Electric field is inversely proportional to square of distance from the charge or an electric dipole.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
Taking Rydberg’s constant
first and second wavelength of Balmer series in hydrogen spectrum is
| (a) 2000 Å, 3000 Å | (b) 1575 Å, 2960 Å | (c) 6529 Å, 4280 Å | (d) 6552 Å, 4863 Å |
A uniform wire of 16 Ω is made into the form of a square. Two opposite corners of the square are connected by a wire of resistance 16 Ω. The effective resistance between the other two opposite corners is
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(a) 32 Ω |
(b) 20 Ω |
(c) 8 Ω |
(d) 4 Ω |
At a certain place, the horizontal component of earth's magnetic field is times the vertical component. The angle of dip at that place is
| (a) 60° | (b) 45° | (c) 90° | (d) 30° |
Assertion : A spark occur between the poles of a switch when the switch is opened.
Reason : Current flowing in the conductor produces magnetic field.
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
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(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
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(c) If assertion is true but reason is false. |
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(d) If the assertion and reason both are false. |
Which of the following helps us in the determination of the temperature of sun
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(a) Kirchhoff's law |
(b) Maxwell Boltzmann law |
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(c) Planck's law |
(d) Stefan's law |