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SSC JE Electrical 2019 with solution SET-2
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The candle power of a lamp placed normal to a working plane is 60 CP. Find the distance if the illumination is 15 lux?

Candle Power of lamp = 60 CP

Illumination of lamp = 15 lux

Distance(D) = ? meters

Illumination of lamp = (candle power)/(distance)2

(D)2 = candle power/Illumination of lamp

(D)2 = 60/15 =4

D = √4

D = 2

SSC JE Electrical 2019 with solution SET-2
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For a three-phase induction motor slip at No Load ÷ slip at Full Load

In terms of slip, the actual speed of the motor (N) can be expressed as

N = Ns(1 − s)

At start, the motor is at rest and hence its speed N is zero.

s = 1 ( start)

This is the maximum value of slip s possible for the induction motor which occurs at start. While s = 0 gives us N = N. which is not possible for an induction motor. So slip of the induction motor cannot be zero under any circumstances.

Practically motor operates in the slip range of 0.01 to 0.05 i.e. 1 % to 5 %. The slip corresponding to the full load speed of the motor is called full load slip.

SSC JE Electrical 2019 with solution SET-2
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The number of valence electrons of P and Si are respectively?

Phosphorus (P) has 15 electron i.e 2,8,5. Hence the number of electron in its outermost orbit is 5.

Silicon (Si) has 14 electron i.e 2,8,4. Hence the number of electrons in its outermost orbit is 4.