EE MCQ

SSC JE Electrical 2019 with solution SET-1
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Identify the INCORRECT statement with regards to synchronous motors

A synchronous motor is not a self-starting motor. You can check out this article why synchronous motor is not self starting

Related Question

SSC JE Electrical 2019 with solution SET-1
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The ratio of conductor voltage and the voltage across the disc nearest to the conductor multiplied by the number discs are

The non -uniformity in the voltage distribution over a string of suspension insulators is expressed in terms of a parameter called “string efficiency“.

The voltage across the unit nearer to the conductor is more than the voltage in the unit nearer to the support. This unequal potential distribution over the string is expressed in terms of string efficiency.

The efficiency of a string is defined as the ratio of voltage across the whole string to the product of the number of discs and the voltage across the disc nearest to the line conductor. Mathematically, it can be expressed as,

Where n = Number of the unit in the string

The more the value of the string efficiency, the more uniform is the voltage distribution across the string. For the ideal case, the string efficiency is 100% and the voltage across each disc of the string is equal. Practically various methods are used to obtain string efficiency as high as possible.

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

SSC JE Electrical 2019 with solution SET-1
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The output of the logic circuit given below represents the gate.

In the given diagram all are NOR Gate . The final output is shown in the figure.

At stage 1 the output will be \overline A \& \overline B

At stage 2 the output will be \overline {\overline A + \overline B } = A.B

And the final output will be \overline {A.B}

Hence for input A & B the output is \overline {AB} in case of Nand gate.

SSC JE Electrical 2019 with solution SET-1
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The direction of the arrow represents the direction of when the diode is forward biased

The direction of the arrow represents the direction of the conventional current flow when the diode is forward biased.