Q81. Magnetic field lines outside a permanent bar magnet travel from:
Basics of Everyday Science: RAS Prelims MCQs
200 RAS Prelims MCQs on the basics of everyday science test the scientific method, the laws of motion, chemical bonding and the cell theory. The questions use daily-life examples, such as the recoil of a gun and the orbit of a satellite, and the explanations give the principle behind each example so that you can reason out similar questions.
Practice questions based on the RPSC RAS Prelims syllabus. They follow the exam pattern but are not past-paper questions.
Showing 81–90 of 200 questions
Q82. Which rule is used to determine the direction of the magnetic field produced by a current-carrying straight conductor?
Explanation
Maxwell’s Right-Hand Thumb Rule is used to determine the direction of the circular magnetic field around a straight current-carrying wire. If the thumb of the right hand points in the direction of the conventional current, the curled fingers indicate the direction of the magnetic field lines. This simple rule is fundamental for understanding the relationship between electricity and magnetism in conductors.
Q83. The most suitable material for making the core of an electromagnet is:
Explanation
Soft iron is the most suitable material for the core of an electromagnet because it is easily magnetized and demagnetized. When electric current flows through the surrounding coil, the soft iron becomes a strong magnet. As soon as the current is switched off, it loses almost all its magnetism quickly. This property allows for precise control over the magnetic field in many applications.
Q84. The phenomenon of generating an electric current in a closed circuit by changing the magnetic field is known as:
Explanation
Electromagnetic induction is the process of generating an electromotive force and subsequently an electric current in a closed circuit by changing the magnetic environment. This can be achieved by moving a magnet relative to a coil or by changing the current in a nearby circuit. Discovered by Michael Faraday, this principle is the foundation for the operation of electric generators and transformers.
Q85. An electric motor works on the principle that:
Explanation
An electric motor operates on the principle that a conductor carrying an electric current will experience a mechanical force when placed within an external magnetic field. The interaction between the magnetic field produced by the current and the external field results in a torque that causes the motor’s rotor to spin. This process effectively converts electrical energy into useful mechanical work or motion.
Q86. Match the laws and rules in List I with their corresponding applications or concepts in List II.
| Law/Rule | Application/Concept |
|---|---|
| A. Fleming’s Left-Hand Rule | i. Magnitude of induced EMF |
| B. Fleming’s Right-Hand Rule | ii. Direction of induced current in generators |
| C. Lenz’s Law | iii. Direction of force on a conductor in motors |
| D. Faraday’s Law | iv. Conservation of energy in induction |
Explanation
Fleming’s Left-Hand Rule determines the force direction in motors, while his Right-Hand Rule finds induced current direction in generators. Lenz’s Law relates induction to the conservation of energy, stating that induced effects oppose their cause. Faraday’s Law provides the mathematical framework for calculating the magnitude of induced EMF. Together, these principles explain how magnetic fields and electric currents interact in technology.
Q87. Who discovered the phenomenon of electromagnetic induction?
Explanation
Michael Faraday was a pioneering scientist who discovered the phenomenon of electromagnetic induction in 1831. Through his experiments with moving magnets and coils, he demonstrated that a changing magnetic field could induce an electric current. This discovery revolutionized science and technology, leading to the development of the electric motor, generator, and transformer, which are essential to modern power systems and electronics.
Q88. Materials like iron, nickel, and cobalt that are strongly attracted by magnets are classified as:
Explanation
Materials like iron, nickel, and cobalt are classified as ferromagnetic because they exhibit strong magnetic properties and are highly attracted to magnets. In these substances, atoms have unpaired electrons that align their magnetic moments in small regions called domains. When exposed to an external magnetic field, these domains align, causing the material to become strongly magnetized and sometimes retain permanent magnetism.
Q89. A device that reverses the direction of current in a circuit periodically is called a:
Explanation
A commutator is a rotary electrical switch used in certain types of electric motors and generators. Its primary function is to periodically reverse the direction of current between the external circuit and the rotating coils. This reversal ensures that the magnetic force continues to pull the rotor in the same direction, allowing for continuous rotation rather than just a partial turn or oscillation.
Q90. Which of the following best describes the Earth’s magnetic north pole?
Explanation
The Earth acts like a giant bar magnet, but its magnetic poles are not identical to its geographic ones. The point referred to as the magnetic north pole actually behaves like the south pole of a magnet. This is why the north-seeking end of a compass needle, which is a north pole, is attracted to and points toward the Earth’s northern regions.Answer key for these questions
| Q | Correct answer |
|---|---|
| 81 | (b) North pole to South pole |
| 82 | (a) Maxwell’s Right-Hand Thumb Rule |
| 83 | (c) Soft iron |
| 84 | (d) Electromagnetic induction |
| 85 | (c) Current-carrying conductors in magnetic fields experience force |
| 86 | (a) A-iii, B-ii, C-iv, D-i |
| 87 | (d) Michael Faraday |
| 88 | (a) Ferromagnetic |
| 89 | (c) Commutator |
| 90 | (a) It behaves magnetically like the south pole of a bar magnet. |
Key facts from Basics of Everyday Science
- Inductive reasoning draws a general conclusion from specific observations; a control variable is kept constant in an experiment; communicating the results is the last step of the scientific method.
- Newton’s second law relates force, mass and acceleration; the recoil of a gun illustrates the third law.
- Momentum is the product of mass and velocity; impulse is equal to the change in momentum.
- A satellite in uniform circular orbit is held by the centripetal force provided by gravity.
- Water (H₂O) and N₂ show covalent bonding; sodium chloride, MgO and CaF₂ are ionic.
- The classical cell theory does not say that all cells have a true nucleus.
Frequently asked questions
How many RAS Prelims practice MCQs are there on Basics of Everyday Science?
This page has 200 practice MCQs on Basics of Everyday Science (Science and Technology). Each has the correct answer, and most have an explanation.
What is the product of mass and velocity called?
Momentum. Newton’s second law says that the rate of change of momentum is equal to the force applied, and impulse is equal to the change in momentum of a body.
Which law explains the recoil of a gun?
Newton’s third law of motion. The gun pushes the bullet forward, and the bullet pushes the gun back with an equal and opposite force, which is felt as recoil.
What holds a satellite in a circular orbit?
The centripetal force provided by gravity. The Earth’s pull keeps changing the direction of the satellite’s velocity so that it moves in a circle and does not fly off in a straight line.