Q.1 Answer the following (MCQ): i) The larger the number of significant figures obtained in a measurement, the ___ accuracy of the measurement. ii) The of the line segment drawn to scale gives the mag

$$
v_g \approx 1.78 \times 10^8 \text{ m/s}
$$
(d) $\boxed{\text{1.78} \times 10^8 \text{ m/s}}$

• ix) The line joining the fictitious North Pole and South Pole of the Earth is called the ______ (a) Magnetic axis

• x) ______ are used in the study of atomic and molecular structure. (c) Radio waves (e.g., in NMR spectroscopy)

Q.2 Answer the following (VSA):

• i) Why do random errors occur? Random errors occur due to unpredictable fluctuations in experimental conditions, such as slight variations in temperature or pressure, or limitations in the observer's judgment and instrument precision. These errors cause measurements to vary randomly around the true value.

• ii) Define free fall. Free fall is the motion of an object solely under the influence of gravity, with no other forces like air resistance acting upon it. In free fall, all objects accelerate downwards at the same rate, regardless of their mass.

• iii) Define perfectly inelastic collision. A perfectly inelastic collision is a type of collision where the colliding objects stick together after impact and move as a single combined mass. In such a collision, the maximum possible amount of kinetic energy is lost, although momentum is still conserved.

• iv) What is gravitational force? Gravitational force is the attractive force that exists between any two objects possessing mass. Its magnitude is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

• v) What is a thermistor? A thermistor is a type of resistor whose electrical resistance is highly sensitive to temperature changes. It is commonly used as a temperature sensor or in temperature-dependent control circuits.

• vi) Optical fibres are immune to EM interference. Explain. Optical fibers transmit information using light signals, which are electromagnetic waves but are confined within the fiber and do not interact with external electromagnetic fields in the same way electrical signals do. Since electromagnetic interference (EMI) primarily affects electrical currents and voltages, optical fibers are immune to such interference, ensuring reliable data transmission in electrically noisy environments.

• vii) What is the disadvantage of cells in parallel? A disadvantage of connecting cells in parallel is that if one cell is faulty (e.g., has a higher internal resistance or is fully discharged), it can draw current from the other healthy cells. This can lead to a faster overall discharge of the battery pack and reduced efficiency, as energy is wasted in the faulty cell.

• viii) Electric vector is also called light vector. Justify. Light is an electromagnetic wave composed of oscillating electric and magnetic fields. The electric field vector is primarily responsible for most optical phenomena, such as absorption, reflection, and refraction, because it interacts much more strongly with the electrons in matter than the magnetic field vector. Due to this dominant interaction, the electric vector is often referred to as the "light vector."