1. William Gilbert
2. Alfred Nobel
3. Joseph Nicephore Niepce
4. Ted Nelson
Option “1” is correct. An electroscope is an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body. It was the first electrical measuring instrument. The first electroscope, a pivoted needle called the versorium, was invented by British physician William Gilbert around 1600.
472. The light with the shortest wavelength is-
1. Red
2. Yellow
3. Blue
4. Violet
Option “4” is correct. Wavelength of red colour is largest and violet colour has the shortest wavelength.
473. Sewing machine was first patented by –
1. Alfred P. Southwick
2. Elias Howe
3. Murasaki Shikibu
4. Hanaoka Seishu
Option “2” is correct. On September 10, 1846, Elias Howe was granted a US patent for his invention of the sewing machine.
474. What is impulse equal to?
1. Change in momentum
2. Change in force
3. Change in velocity
4. Change in acceleration
Option “1” is correct. The impulse-momentum theorem states that the change in momentum of an object equals the impulse applied to it.
475. ISRO built India’s first satellite known as _____.
1. Aryabhatta
2. Bhaskara
3. Rohini
4. Insat 1A
Option “1” is correct. ISRO built India’s first satellite known as Aryabhata.
476. In a projectile motion, a large angle with the horizontal produces ______.
Option “4” is correct. In a projectile motion, a large angle with the horizontal produces high trajectory.
477. 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.
478. Which one of the following is not correctly matched?
1. Knot – Unit to Measure speed of ship
2. Nautical mile – Unit of distance used in navigation
3. Angstrom – Unit of length
4. Light year – Unit of measuring time
Option “4” is correct. Light year is not a unit of measuring time, but a unit of measuring distance. The remaining pairs are correctly matched.
479. Which one of the following is not the unit of heat?
1. Calorie
2. Kilocalorie
3. Kilojoule
4. Watt
Option “4” is correct. The watt is a derived unit of power in the International System of Units (SI). Rest of all are the units of heat.
480. The technique used to transmit audio signals in television broadcast is-
1. Amplitude modulation
2. Pulse code modulation
3. Frequency modulation
4. Time dimension multiplication
Option “3” is correct. Television broadcasts emit two types of signals, audio and visual. These two signals require modulation to transmit both signals at the same time. Analog television requires transmission that uses specific modulation methods employing AM and FM signals in its transmission. Frequency modulation or FM is used for the audio part of the transmission. Amplitude modulation or AM is used in the video transmission.
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