Tag: lightning safety

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Multiple choice physics some natural phenomena lightning conductors lightning safety advanced of lightning

What is earthing?

  1. Passage of large electric current resulting from a lightning into the earth

  2. Burying electric charge into the earth

  3. Preventing electric charge from entering the earth

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A lightning conductor a device used to prevent tall buildings from being struck by lightning. It is fixed on the top of tall buildings with one end at the top having several sharp metal spikes that attract lightning. This is connected to a copper strip. The other end of the strip is attached to a large metal plate buried deep into the ground causing the electric charge to flow into the earth. This process is called earthing.

Multiple choice physics some natural phenomena lightning conductors lightning safety advanced of lightning


Two types of earthings are provided: (a) Equipment earthing and (b) Neutral point earthing. Equipment earthing is provided for

  1. Safety of human being

  2. Safety of equipments

  3. Safety of starters and cables

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Equipment earthing is a connection done through a metal link between the body of any electrical appliance, or neutral point, as the case may be, to the deeper ground soil. The metal link is normally of MS flat, CI flat, GI wire which should be penetrated to the ground earth grid.

  • Safety of personnel
  • Safety of equipment Prevent or at least minimize damage to equipment as a result of flow of heavy currents.
  • Improvement of the reliability of the power system

Option A is correct.

Multiple choice physics some natural phenomena lightning conductors lightning safety advanced of lightning

A lightning conductor installed in a building

  1. does not allow the lightning to fall on the building

  2. repels the lightning

  3. forces the lightning to fall in an area where there are no buildings

  4. conducts electric charge to the ground when lightning strikes the building
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A lightning conductor is generally made of metal spikes , which are connected to ground through a copper wire . The spikes are pointed , hence electric field strength is strong around pointed spikes . Due to this intense electric field , spikes conduct electric charge easily to the ground when lightning strikes he building .

Multiple choice physics some natural phenomena lightning conductors lightning safety advanced of lightning

Electric field in the region is given as $E=(10-5x)i$. A charge of the mass 5 kg and charge Q (=1 C) is situated at origin and free to move in given electric field, then choose the correct option (neglect gravity).

  1. motion of charge particle is oscillatory

  2. maximum displacement of charge particle from origin is 4 SI units

  3. maximum velocity gain by charge particle is 2 SI units

  4. the position of charge particle, when velocity gained by particle is maximum is 2 SI units
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Force F = qE = 1 * (10-5x) = 10-5x. Acceleration a = F/m = (10-5x)/5 = 2-x. Velocity v dv/dx = 2-x. Integrating, v^2/2 = 2x - x^2/2. Max velocity occurs when a=0, i.e., x=2. At x=2, v^2/2 = 4 - 4/2 = 2, so v=2.

Multiple choice physics some natural phenomena lightning conductors lightning safety advanced of lightning

Buildings are more susceptible to a lightning strike because

  1. they are higher than their surroundings.

  2. roofs of buildings are wet in rainy season and hence become good conductors of electricity.

  3. the top of the building is wet and acquires an opposite charge to a cloud passing over the top by induction.

  4. All of the above.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Buildings are highly susceptible to a lightning strike because of the following reasons:

1. They are higher than their surroundings and closer to the clouds.
2. The roofs of buildings are wet in rainy season and hence become good conductors of electricity.
3. The top of the building is wet and acquires an opposite charge to a cloud passing over the top by induction.