Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
1. Ohm is a unit of measuring _________?
[A] Resistance
[B] Voltage
[C] Current
[D] None of the above
Show Answer
Correct Answer: A [Resistance]
Notes:
The ohm is the SI unit of electrical resistance. Electrical resistance of an object is the measure of its obstruction to the flow of electric current. It mainly depends on the material it is made of, cross sectional area of a conductor, length and temperature. The resistance of a conductor of unit cross-sectional area and unit length is known as Resistivity. The unit of resistivity is ohm-metre.
2. When two mercury drops are brought into contact they form a single bigger drop to get which of the following?
[A] Minimum volume
[B] Minimum surface area
[C] Maximum size
[D] Maximum surface area
Show Answer
Correct Answer: B [Minimum surface area]
Notes:
When two drops of mercury come into contact, they will tend to merge together and form a single drop with a minimum surface area. This is because of the properties of mercury, which is a liquid metal with a high surface tension. The surface tension of a liquid is a measure of its elasticity, and it is determined by the cohesive forces between the molecules of the liquid. In the case of mercury, the high surface tension causes the molecules at the surface of the liquid to be strongly attracted to each other, which results in the formation of a relatively smooth and spherical surface. When two drops of mercury are brought together, the surface tension causes them to merge and form a single drop with the smallest possible surface area. This phenomenon is known as the “minimization of surface area” and it is a common feature of liquids with high surface tension.
3. Which of the following is an instrument for measuring electric charge or electrical potential difference?
[A] Ammeter
[B] Voltmeter
[C] Electrometer
[D] ohmmeter
Show Answer
Correct Answer: B [Voltmeter]
Notes:
Voltmeter is an instrument for measuring electric charge or electrical potential difference. It was invented by Hans Christian Oersted.
4. A vehicle moving on a circular path experiences ________?
[A] centripetal force
[B] centrifugal force
[C] gravitational force
[D] None of the above
Show Answer
Correct Answer: A [centripetal force]
Notes:
A vehicle moving on a circular path experiences centripetal force. Centripetal force that acts on a body moving in a circular path and is directed towards the centre around which the body is moving.
5. Which among the following correctly represents a Parsec?
[A] 0.326 Light Years
[B] 3.261 Light Years
[C] 32.61 Light Years
[D] 3.026 Light Years
Show Answer
Correct Answer: B [3.261 Light Years]
Notes:
One parsec is approximately equal to 31 trillion kilometres (19 trillion miles), or 210,000 astronomical units, and equates to about 3.3 light-years.
6. Which among the following is the SI physical unit of dynamic viscosity?
[A] Poise
[B] Pascal-second
[C] Newton-second
[D] Poise-second
Show Answer
Correct Answer: B [Pascal-second]
Notes:
The SI unit for dynamic viscosity η is the Pascal-second (Pa-s). It corresponds to the force (N) per unit area (m2) divided by the rate of shear (s-1).
7. Which of the following waves is called compression-dilation waves or longitudinal waves?
[A] Primary waves
[B] Secondary waves
[C] Love waves
[D] Rayleigh waves
Show Answer
Correct Answer: A [Primary waves]
Notes:
Primary wave is also called compression-dilation or longitudinal waves. Secondary wave is called transversal wave. Love wave and Rayleigh wave are surface waves. P waves can pass through solid, liquid and gases and are also the fastest among the three main types of waves.
8. The alpha radiation is not used in radiotherapy because:
[A] It is an ionizing radiation
[B] It is unable to penetrate human skin
[C] It is toxic to human tissues
[D] It is not cost effective
Show Answer
Correct Answer: B [ It is unable to penetrate human skin]
Notes:
Alpha radiation is not used in radiotherapy because it cannot penetrate human skin. Alpha particles are a highly ionizing form of particle radiation with a short range. They can be stopped by a few centimeters of air or by skin. This means that external therapy would be useless because the alpha radiation would not be able to enter the body. Alpha particles have a very large atomic volume. They are given additional mass by the two neutrons they contain. This facilitates ionization by coulombic interaction or direct collision of the alpha particle with atomic electrons. Radiation therapy is a treatment that uses ionizing radiation to kill or control the growth of malignant cells. It is often delivered by a linear particle accelerator.
9. Echoes are heard when we shout in an empty hall. But when the hall is full of people no echoes are heard why?
[A] Echoes are subdued in the noise of people
[B] Soft clothes of people absorb sound instead of reflecting it
[C] Destructive interference of sound takes place
[D] Excessive reverberations take place
Show Answer
Correct Answer: D [ Excessive reverberations take place]
Notes:
When we shout in an empty hall, we hear your own sound after a short time. This is because the empty room reflects the sound, so there is an echo.
When a hall is full of people, the sound produced is reflected multiple times by the people. This causes the sound to overlap with the original sound, so the listener can’t distinguish between the two.
For an echo to be heard, the surfaces need to reflect the sound, or there needs to be more clarity. For example, big open spaces are good for hearing echoes.
10. Which of the following branch of Physics deal with study of Atomic Nuclei?
[A] Nuclear Physics
[B] Bio Physics
[C] Atomic Physics
[D] None of the above
Show Answer
Correct Answer: A [Nuclear Physics]
Notes:
Nuclear physics is a branch of physics that deals with the constituents, structure, behaviour and interactions of atomic nuclei. Atomic physics is a branch of physics that deals with the composition of the atom apart from the nucleus