Tag: science & technology

Quizzes (551) Questions (11015)

Questions Related to science & technology

Multiple choice general knowledge science & technology

The armature of a dc motor iis laminated

  1. to reduce hysteresis loss

  2. to reduce eddy current loss

  3. to reduce the cost of core

  4. to reduce the mass of the armature
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The armature of a DC motor is laminated to reduce eddy current loss. Laminations break up the path of circulating eddy currents by introducing insulation between layers, significantly reducing these parasitic currents and the associated heating losses.

Multiple choice general knowledge science & technology

Interpole winding in a dc generator is proportional to

  1. a large number of turns of thin wire

  2. a small number of turns of thick wire

  3. a lage number of turns of thick wire

  4. a small number of turns of thin wire
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Interpole winding in a DC generator uses a small number of turns of thick wire. Interpoles (commutating poles) carry armature current to neutralize reactance voltage, requiring low resistance and high current capacity - hence thick wire with few turns.

Multiple choice general knowledge science & technology

The armature mmf waveform in a dc machine is

  1. pulsating

  2. rectangular

  3. triangular

  4. sinusoidal
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The armature MMF waveform in a DC machine is triangular in shape. This is because the armature conductors are distributed in slots, creating a MMF distribution that varies linearly across the pole face, forming a triangular pattern rather than sinusoidal or rectangular.

Multiple choice general knowledge science & technology

Consider the following scenario : 'A cat accidentally drops from the seventh floor of a high rise. It does not face any casualty, infact it is perfectly alright, because of it's well padded paws. But the same cat fell down from the third floor some days later and suffered a few bruises.' Please select the correct reason from the below options : [Hint:- Try fluid mechanics]

  1. There was too much wind the second day for the cat to settle down

  2. The cat was fatigued out due to repetitve accidents

  3. The cat tried a different way of landing and failed

  4. The air friction in the first case helped the cat
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The cat survives falls from higher floors because air resistance (drag) increases with speed, leading to a terminal velocity. From the seventh floor, the cat reaches terminal velocity and can orient itself to land properly. From the third floor, it hasn't reached terminal velocity and has less time to right itself.

Multiple choice general knowledge science & technology

General emf and current are in the same direction in case of

  1. series motors

  2. shuntmotors

  3. dc generators

  4. all of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In DC generators, the generated emf and armature current flow in the same direction - both leave the positive terminal during generation. This is the fundamental principle of generator operation. In motors, the emf (back emf) opposes the current flow. Series and shunt motors consume electrical power, so their emf opposes current.

Multiple choice general knowledge science & technology

The swinging of the leather ball in cricket can be explained through -

  1. Poissons Ratio

  2. Navier-Stokes

  3. Bernoulli's equation

  4. Euler equations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cricket ball swing is caused by pressure difference on the two sides of the ball due to asymmetric airflow over the seam. Bernoulli's equation explains how faster-moving air creates lower pressure, causing the ball to swing toward the side with higher pressure. Navier-Stokes and Euler equations govern fluid flow but are unnecessarily complex for this phenomenon.

Multiple choice general knowledge science & technology

In case starting resistance of a series motor is short circuited, the motor will

  1. burn out

  2. not start

  3. run at very high speed

  4. run with excessive speed
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When starting resistance of a series motor is short-circuited, the motor receives full voltage immediately, causing very high current and torque. This excessive torque makes the motor run at dangerously high speeds, which can damage the motor. The starting resistance is meant to limit initial current and prevent this unsafe condition.