# Physics GK Quiz-41

## Physics GK Quiz-41

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

### 801. Flemings “Left hand Rule” is associated with the effect of

(1) Electric field on current
(2) Magnetic field on magnet
(3) Electric field on magnet
(4) Magnetic Field on current
Answer:
801. (4) Whenever, a current carrying conductor comes under a magnetic field, there will be force acting on the conductor and on the other hand, if a conductor is forcefully brought under a magnetic field, there will be an induced current in that conductor. In both of the phenomenon, there is a relation between magnetic field, current and force. This relation is directionally determined by Fleming Left Hand rule and Fleming Right Hand rule respectively.

### 802. The force which makes a vehicle to stop when break is applied is called

(1) gravitational force
(2) vanderwalls force
(3) frictional force
(4) covalant force
Answer:
802. (3) A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. When the brakes are applied, work is done by the friction force between the brakes and the wheels.

### 803. Why is weightlessness experienced while orbiting the earth in space ships ?

(1) Inertia
(2) Acceleration
(3) Zero gravity
(4) Orbital motion
Answer:
803. (*) The reason astronauts experience weightlessness which orbiting the earth in spaceships is that they are in free fall. A spacecraft in orbit is falling towards the Earth, because of gravity, but it is moving forward in its orbit fast enough that the path it follows is a curve that is a closed ellipse. Hence, the astronaut is not able to exert his mass on its surface. This condition is called weightlessness condition.If the spacecraft does not move quickly enough, it would fall prey to the effects of earth’s gravitational field and fall to the earth. Contrary to common misconception, there is no such thing as ‘Zero Gravity.’ Gravity is everywhere in the universe and manifests itself in black holes, celestial orbits, ocean tides, and even our own weight. The International Space Station, the space shuttle, and satellites are designed to stay in orbit, neither falling to the ground nor shooting off into space. Best option : (4) Orbital Motion

### 804. Where is a transistor most likely to be found ?

(1) Wrist watch
(2) Fuse
(3) Hearing aid
(4) Fluorescent lamp
Answer:
804. (3) A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.The transistor invented in 1948 was well suited to the hearing aid application due to low power and small size; hearing aids were an early adopter of transistors. Transistors replaced the need for batteries in hearing aids.

### 805. Every hot object emits _____

(1) X–rays
(2) Visible light
(3) Infrared rays
(4) Ultraviolet rays
Answer:
805. (3) As per Planck’s law, all objects emit electromagnetic radiation according to their temperature. Colder objects emit waves with very low frequency (such as radio or microwaves), while hot objects emit infrared rays or even ultraviolet and higher frequencies.At room temperature, most of the radiation is in the infra-red region.

### 806. In hydel power station, the motion produced in turbines is due to

(1) flow of water
(2) burning of coal
(3) burning of diesel
(4) production of steam
Answer:
806. (1) A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work.Hydroelectric power comes from water at work, water in motion. To generate electricity, water must be in motion. This is kinetic (moving) energy. When flowing water turns blades in a turbine, the form is changed to mechanical (machine) energy. The turbine turns the generator rotor which then converts this mechanical energy into another energy form — electricity.

### 807. Two vectors are said to be equal if

(1) only their magnitudes are same
(2) only their directions are same
(3) both magnitude and direction are same
(4) magnitudes are same but directions are opposite
Answer:
807. (3) If the magnitude as well as direction of two vectors are equal, then they are known as equal vectors. In other words, two vectors are said to be equal, if they possess equal magnitude and are headed towards the same direction. For two equal vectors, their directed line segments must be parallel.

### 808. Fuse wire is made of an alloy of

(1) Tin and Lead
(2) Tin and Copper
(3) Lead and Copper
(4) Copper and Silver
Answer:
808. (1) The common material used as fuse wire is an alloy of tin and lead (63% tin and 37% lead). Fuse wires provide overcurrent protection of an electrical circuit including the source of power and the load. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby interrupting the flow of current.

### 809. Which of the following has the lowest frequency?

(1) Visible light
(2) Gamma rays
(3) Xrays
(4) Ultra violet rays
Answer:
809. (1) The electromagnetic spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and frequency: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.So among the given options, visible lights has the lowest frequency, while gamma rays has the highest.

### 810. A fresh egg when placed in salt water will

(1) sink and go to the bottom
(2) sink but will not go to the bottom
(3) float
(4) burst
Answer:
810. (3) When a fresh egg is placed in regular water, it sinks. However, when the same egg is placed in saltwater, it floats. This is because salt water is denser than the egg causing it to float.

### 811. Which one among the following is not an electromagnetic wave?

(1) X-Ray
(2) R-Ray
(3) Cathode Ray
(4) Infrared Ray
Answer:
811. (3) In physics, electromagnetic radiation (EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-, and gamma radiation.

### 812. Which one of the following is a good electrical conductor?

(1) Graphite
(2) Diamond
(3) Peat
4) Charcoal
Answer:
812. (1) Graphite is a good conductor of electricity because its electrons are delocalized or free to move around. Each carbon atom in graphite is directly linked to only three carbon atoms through covalent bonds. Therefore, out of the four valence electrons in a carbon atom, only three are used for bonding and the fourth is relatively free and can move from one carbon atom to the other.

### 813. Sending a frame to a group of stations is known as

(1) Single casting
(2) Spreading
(3) Multicasting
(4) Casting
Answer:
813. (3) In addition to transmitting frames directed to a single address, local area networks are capable of sending frames directed to a group of address, called a multicast address, which can be received by a group of stations.They can also send frames directed to all stations using the broadcast address. A frame sent to multicast destination address can be received by all stations configured to listen for that multicast address.

### 814. Which one among the following components can not be developed within an “integrated circuit”?

(1) Diode
(2) Triode
(3) Transformer
(4) Transistor
Answer:
814. (3) Some components like transformers and inductors cannot be integrated into an IC except for very specialized high frequency applications. They have to be connected externally to the semiconductor pins. In general, transformers are located in circuit boards as separate components and cannot be integrated into semiconductor based integrated circuits.

### 815. A particle is thrown vertically upward. When it reaches the highest point, it has

(1) a downward acceleration
(2) an upward acceleration
(3) a downward velocity
(4) a horizontal velocity
Answer:
815. (1) When a particle is thrown vertically upwards in space, it will experience constant acceleration towards the ground (irrespective of the direction in which it is moving in), known as acceleration due to gravity. At the highest point, it has zero velocity but has downward acceleration equal to acceleration due to gravity.

### 816. The quality or tone of a musical sound produced by a stringed instrument depends on

(1) frequency of vibration
(2) length of the strings in the instrument
(3) Amplitude of vibration
(4) wave form of the sound
Answer:
816. (4) The timbre or quality of a sound depends on its wave form, which varies with the number of overtones, or harmonics, that are present, their frequencies, and their relative intensities. In simple terms, timbre is what makes a particular musical sound have a different sound from another, even when they have the same pitch and loudness.

### 817. Why does a cannon recoil after firing ?

(1) Conservation of energy
(2) Backward thrust of gases produced
(3) Newton’s third law of motion
(4) Newton’s first law of motion
Answer:
817. (3) Recoil is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gases (ejecta), According to Newton's third law. In case of canons, the momentum is transferred to the ground through its mount.

### 818. A bomb explodes on the moon. You will hear its sound on earth after ______

(1) 20 minutes
(2) 2 hours 20 minutes
(3) 3.7 hours
(4) You cannot hear the sound of explosion
Answer:
818. (4) The sound will never reach Earth because there are not enough molecules or atoms of matter per cubic centimeter of space to create the pressure waves in a medium that is a sound wave. In simple
words, Sound propagation needs a medium. The people on the Earth can see the flash, but no sound.

### 819. Person who is colour blind cannot distinguish between

(1) Black and yellow
(2) Red and green
(3) Yellow and white
(4) Green and blue
Answer:
819. (2) Color blindness is the decreased ability to see color or differences in color. The most common form of colour blindness is known as red/green colour blindness and most colour blind people suffer from this. Those affected have difficulty with discriminating red and green hues due to the absence or mutation of the red or green retinal photoreceptors.

### 820. During the motion of a projectile fired from the earth surface, _______

(1) its kinetic energy remains constant
(2) its momentum remains constant
(3) vertical component of its velocity remains constant
(4) horizontal component of its velocity remains constant
Answer:
820. (4) The motion of a projectile is a two-dimensional motion—Horizontal motion and vertical motion—that take place independent of each other. The horizontal velocity of a projectile is constant (a never changing in value). The force of gravity continuously affects the vertical component, so the vertical motion is a uniformly accelerated motion.