231. A device which converts electrical energy into mechanical energy is-
1. Dynamo
2. Transformer
3. Electric motor
4. Inductor
Option “3” is correct. Electric motor is a device which converts electrical energy into mechanical energy. Electric motors involve rotating coils of wire which are driven by the magnetic force exerted by a magnetic field or an electric current.
232. Electric motors operating at low voltages tend to burn out because-
1. They draw more current which is inversely proportional to the voltage.
2. They draw more current which is inversely proportional to the square root of the voltage.
3. They draw heat proportional to V2.
4. Low voltage sets in electrical discharge.
Option “1” is correct. Electric motors operating at low voltage tend to burn out because they draw more current which is inversely proportional to the voltage.
233. Reflection from a smooth surface like that of a mirror is called ___________ reflection.
1. Regular
2. Irregular
3. Diffused
4. Fused
Option “1” is correct. When a beam pass of parallel light rays is incident on a smooth and plane surface, the reflected rays will also be parallel. This type of reflection is called Regular Reflection.
234. Which of the following is not a vector quantity?
1. Momentum
2. Displacement
3. Torque
4. Speed
Option “4” is correct. Speed is the distance travelled by object in a certain interval of time.Speed is not dependent on direction hence it is a scalar quantity. While Displacement, Momentum and Torque has both magnitude and direction, so they are vector quantity.
235. At what temperature (in Fahrenheit) pure water freezes?
1. 32
2. 0
3. 48
4. 37
Option “1” is correct. The temperature at which a liquid freezes is called the Freezing Point. The freezing point of water is 32°F.
236. What is the other name of Galileo’s law of falling bodies?
1. Law of motion
2. Newton’s first law
3. Newton’s second law
4. Newton’s third law
Option “2” is correct. Newton’s first law is other name of Galileo’s law of Falling bodies.According to Law of Fall “The distance travelled by falling body is directly proportional to the square of the time it takes to fall”. This latter claim states that a body in motion will continue its motion so long as no factor disturbs that motion. This principle is called the principle of inertia which is basis of Newton’s first law.
237. Which one among the following components is used as an amplifying device?
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