Physics

One horsepower (hp) is defined as exactly 746 watts (W). This is a standard conversion used in physics and engineering to relate mechanical power to electrical power.

Work done by a variable force is determined by dividing both the force and displacement into small intervals and summing the product of force and displacement over these intervals, effectively calculating the integral of force over displacement.

Steel has the highest elasticity among the given substances because it has a high Young's modulus, meaning it can undergo significant stress with minimal strain before deforming permanently. Rubber, glass, and copper have lower elastic moduli compared to steel.

Young's modulus is calculated using the formula Y = (F/A) / (ΔL/L). Given F = 10 N, A = 2 cm² = 2×10⁻⁴ m², L = 1 m, and ΔL = 0.01 m, substituting these values yields Y = (10 / 2×10⁻⁴) / (0.01 / 1) = 5×10⁶ N/m², which corresponds to option B.

Photovoltaic cells convert solar energy directly into electrical energy by the photovoltaic effect, making option B correct. Rotary and galvanic cells do not perform this function, and 'non of these' is incorrect.

Tidal energy is generated primarily due to the gravitational pull of the Moon on Earth's oceans, causing tides. While the Sun also influences tides, the Moon's effect is dominant, making it the main source of tidal energy.

A conservative field is defined as a field in which the work done in moving a body along any closed path is zero. This is a fundamental property distinguishing conservative fields from non-conservative ones.

Young's modulus (also called the modulus of elasticity) is defined as the ratio of stress to strain within the elastic limit of a material under tension or compression. Stress is the force per unit area applied, and strain is the relative change in length (extension/original length). Young's modulus is a constant for a given material in the elastic region, representing how stiff the material is. It is not proportional to strain; rather, it is the constant ratio stress/strain. Therefore, the correct interpretation is that Young's modulus is the ratio of stress to strain, making option B correct.

Deformation refers to any change in shape, length, or volume of a body when subjected to an external force, which matches the definition given in the question.

Coercive force is the magnetic field strength required to reduce the magnetization of a material to zero after it has been magnetized; thus, it opposes demagnetization.