Q1. What is the SI unit of electric current?
Q2. Which phenomena shows the particle nature of light?
(c) Photoelectric effect
Q3. Electric Motor converts _____ energy to mechanical energy.
Q4. Optical ﬁbre works on which of the following principle of light?
(d) Total internal reflection
Q5. Who invented the thermos flask?
(a) Ray Tomlinson
(b) Tim Berners-Lee
(c) William Cullen
(d) James Dewar
Q6. Friction is caused by the ______________ on the two surfaces in contact.
Q7. The motion of a freely falling body is an example of ________________________ motion.
(a) Uniformly accelerated
(b) Non-uniformly accelerated
(c) Constant velocity
(d) Constant speed
Q8. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its ___________.
(b) Melting point
Q9. For an object, the state of rest is considered to be the state of ______ speed.
Q10. The laws which govern the motion of planets are called ___________________.
(a) Newton’s Laws
(b) Kepler’s Laws
(c) Avogadro’s Laws
(d) De Morgan’s Laws
Sol. The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.
Sol. The photoelectric effect is an phenomenon in which the emission of electrons occurs when a beam of light strikes a metal or a cathode surface. For emissions of electrons frequency of incident light is required to be greater than a minimum value called Threshold Frequency. Thus, show particle nature of light.
Sol. An electric motor is an electrical machine that converts electrical energy into mechanical energy.
Sol. Optical fibre work on the principle of Total Internal Reflection of Light. In optical fibre, when light traveling in an optically dense medium hits a boundary at a steep angle (larger than the critical angle for the boundary), the light is completely reflected. This is called total internal reflection.
Sol. In 1892, Scottish scientist Sir James Dewar invented the thermos flask.
Sol. Friction is caused by the irregularities on the two surface in contact.
Sol.In general, a uniformly accelerated motion is the one in which the acceleration of the particle throughout the motion is uniform. The motion of a freely falling body is an example of Uniformly accelerated motion.
Sol.The Melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure.
Sol. For an object, the state of rest is considered to be the state of zero speed.
Sol. The laws which govern the motion of planets are called Kepler’s law of planetary motion.
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