Q71. According to Ohm’s law, at a constant temperature, the current flowing through a conductor is directly proportional to the:
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 71–80 of 200 questions
Q72. If three resistors of 2 ohms, 3 ohms, and 5 ohms are connected in series, the equivalent resistance is:
Explanation
When resistors are connected in a series circuit, the total or equivalent resistance is simply the sum of the individual resistances. In this case, adding the values of two ohms, three ohms, and five ohms yields a total resistance of ten ohms. This arrangement ensures that the same current flows through each resistor, while the total voltage is divided among them.
Q73. Which of the following instruments is used to measure electric current in a circuit?
Explanation
An ammeter is a specialized electrical instrument designed to measure the rate of electric current flowing through a circuit. It is calibrated to provide readings in Amperes, the standard unit of current. To accurately capture the flow of electrons, it must be integrated directly into the circuit path so that the entire current passes through the device for measurement.
Q74. An ammeter is always connected in a circuit in:
Explanation
To measure the total electric current in a specific branch or circuit, an ammeter must always be connected in series. This ensures that the full flow of charge passes through the instrument. Ammeters are designed with very low internal resistance to minimize their impact on the overall circuit, preventing a significant drop in current that would occur with high-resistance devices.
Q75. Consider the following statements about the resistance of a metallic wire:
I. It is directly proportional to its length.
II. It is inversely proportional to its area of cross-section.
III. It depends on the nature of the material.
IV. It remains unaffected by temperature changes.
V. Resistance increases if the wire is stretched.
Which of the above statement(s) is/are incorrect?
I. It is directly proportional to its length.
II. It is inversely proportional to its area of cross-section.
III. It depends on the nature of the material.
IV. It remains unaffected by temperature changes.
V. Resistance increases if the wire is stretched.
Which of the above statement(s) is/are incorrect?
Explanation
The resistance of a metallic wire is influenced by its physical dimensions and material properties. It is directly proportional to length and inversely proportional to the cross-sectional area. Stretching a wire increases length and decreases area, raising resistance. Crucially, resistance is not constant with temperature; for most metals, it increases as the temperature rises, making the statement about temperature independence incorrect.
Q76. The domestic electrical supply in India generally uses Alternating Current (AC) at a frequency of:
Explanation
In India, the standard domestic electrical power supply provides alternating current at a frequency of fifty Hertz. This means the direction of the current changes one hundred times every second. Additionally, the standard voltage for home use is typically two hundred and twenty volts. This frequency and voltage combination is used to ensure compatibility and efficiency across the national electrical grid.
Q77. The principle of working of an electric fuse is based on the:
Explanation
An electric fuse is a critical safety device designed to protect circuits from excessive current. Its operation is based on the heating effect of electric current. The fuse contains a wire with a low melting point; when the current exceeds a safe limit, the heat generated causes the wire to melt and break the circuit, preventing damage to appliances and electrical fires.
Q78. According to Joule’s law of heating, the heat produced in a resistor is proportional to the:
Explanation
Joule’s law of heating quantifies the thermal energy produced when an electric current passes through a conductor. It states that the heat generated is directly proportional to the square of the current, the resistance of the conductor, and the time for which the current flows. Because of the squared relationship, even a small increase in current leads to a much larger increase in heat.
Q79. Materials that offer zero electrical resistance at extremely low temperatures are called:
Explanation
Superconductors are unique materials that exhibit exactly zero electrical resistance when cooled below a specific critical temperature. In this state, they can carry electric current indefinitely without any loss of energy as heat. This phenomenon also allows them to expel magnetic fields, a property known as the Meissner effect, which has significant applications in advanced technologies like magnetic levitation and medical imaging.
Q80. Given below are two statements: one is labelled as Assertion (A) and the other is labelled as
Reason (R).
Assertion (A): Silver is not used for making standard electrical transmission wires despite being the best conductor of electricity.
Reason (R): Silver is highly expensive and prone to theft compared to copper and aluminum.
Reason (R).
Assertion (A): Silver is not used for making standard electrical transmission wires despite being the best conductor of electricity.
Reason (R): Silver is highly expensive and prone to theft compared to copper and aluminum.
Explanation
Silver is the most efficient conductor of electricity due to its high electron mobility. However, it is not used for large-scale power transmission because its high cost makes it economically unfeasible. Copper and aluminum offer a better balance of high conductivity, lower cost, and abundance. Additionally, using silver would significantly increase the risk of theft from utility infrastructure due to its value.Answer key for these questions
| Q | Correct answer |
|---|---|
| 71 | (d) Potential difference across its ends |
| 72 | (a) 10 ohms |
| 73 | (c) Ammeter |
| 74 | (a) Series |
| 75 | (c) IV only |
| 76 | (a) 50 Hz |
| 77 | (c) Heating effect of current |
| 78 | (d) Square of the current |
| 79 | (a) Superconductors |
| 80 | (a) Both A and R are true and R is the correct explanation of A. |
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.