HVE unit 1

The electrical field developed within clouds before a lightning stroke occurs can be of the order of

• 0.1 kV/cm

• 1 kV/cm

• 100 kV/cm

• 10 kV/cm

The maximum voltage gradient at the ground level due to a charged cloud before lightning strikes, can be as high as

• 1 V/cm

• 30 V/cm

• 30 V/m

• 300 V/cm

The velocity of wind currents required for charge separation inside the moving clouds is of the order

• 1 to 5 m/s

• 5 to 10 m/s

• 10 to 20 m/s

• 50 to 200 m/s

Velocity of leader strokes in lightning discharges is about

• 1.5 × 105 cm/s

• 1.5 × 106 cm/s

• 1.5 × 107 m/s

• 1.5 × 108 m/s

The velocity of return or main stroke may be of the order of (C = velocity of light)

• 0.01 C

• 0.001 C

• 0.1 C

• 0.8 C

The peak value of lightning stroke currents are of the order

• 100 A

• 1000 A

• 10 to 100 kA

• 106 A

The cumulative probability of a 10 kA lightning stroke current ( peak) is about(A)

(B)

(C)

(D)

• 0.6

• 0.2

• 0.1

• 0.98

The rate of rise of current (di/dt) in lightning strokes is

• 1 kA/µs

• 100 kA/µs

• 100 A/µs

• 1000 kA/µs

The ground flash over density (N g) in any region due to lightning activity is about (TD=Thunderstorm days)

• 0.1 to 0.2 TD/km2-year

• 1 to 2 TD/km2-year

• 30 to 50 TD/km2-year

• 5 to 15 TD/km2-year

Surge impedance of lossless transmission line is (if L= inductance/m, C= capacitance/m)

• √C/L

• √L/C

• √LC

• 2√LC