EE MCQ

SSC JE Electrical 2019 with solution SET-1
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Two bulbs of rating 230V, 60W, and 230V, 100W are connected in parallel across supply mains, Identify the correct statement

For Bulb 1

Power = 60 W

Voltage = 230 V

R = V2/P

R = (230 × 230)/60

R = 881.66 Ω

For Bulb 2

Power = 230 W

Voltage = 120 V

R = V2/P

R = (230 × 230)/100

R = 529 Ω

In a parallel connection, the voltage across each element is the same. So when a 60W bulb and 1o0 W bulb are connected in parallel, the voltage across them will be the same i.e 230 V in the given case. To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation

P = V2/R

Since the voltage is the same we can say that power dissipation will be higher for the bulb with lower resistance i.e. 100W bulb, or the bulb with the higher rating will glow brighter.

In a series connection, the current flowing across each element is the same. So when the 60W bulb and 100W bulb are connected in series, the same current will flow through them. To find which bulb will glow brighter we need to find the power dissipation across each of them. From the relation

P = I2R

Related Question

SSC JE Electrical 2019 with solution SET-1
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4F2D is a/an number

The hexadecimal number system is also called base-16, a numeration system in which all numbers are represented using the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F only. The system is base of 16. The hexadecimal numbers are used to represent binary numbers because of ease of conversion and compactness.

SSC JE Electrical 2019 with solution SET-1
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Which of the following fuel has the least calorific value?

In the above option, the wood has the lowest calorific value. Its value is around 17000 – 20000 kilojoule/kg.

The calorific value of LPG is 55000 kilojoule/kg.

The calorific value of Kerosene oil is 45000 kilojoule/kg.

The calorific value of hydrogen oil is 150000 kilojoule/kg.

SSC JE Electrical 2019 with solution SET-1
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Hysteresis loss is NOT a function of

Hysteresis Loss = Kh × BM1.67 × f × v watts

where

Kh = Hysteresis constant depends upon the material

Bm = Maximum flux density

f = frequency

v = Volume of the core

Hence the hysteresis loss does not depend upon the ambient temperature.

SSC JE Electrical 2019 with solution SET-1
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A synchronous motor runs at 600rpm, which of the following case is true?

Synchronous speed NS = 120f/P

When

P = 12 & F = 60 then Ns = ?

NS = 120f/P = (120 × 60)/12 = 600 RPM