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Answer: Option D Refer to the video explanation

Brightness of the filament bulb depends on power. The design of the filament is such that it uses tungsten (high resistivity), coil up (to increase the length) and thin tungsten filament (small cross-sectional area). These features are to let the tungsten filament achieve a certain amount of resistance, so that when current flows through, energy is transferred electrically to the internal (thermal) store of the filament, so that it is hot and the filament glow and gives out light. But a misconception is - the higher the resistance of the filament, the hotter it is, the brighter the bulb will be. This is WRONG.

There are factors that affect resistance of the filament (conductor): length cross-sectional area Resistivity For our syllabus, brightness of the bulb depends on power. The higher the power, the brighter the bulb. e.g. a 100 W bulb is brighter than a 60 W bulb, View the video to understand the concepts better Video

For Science Physics, you just need to the I-V graphs of ohmic conductor e.g fixed resistor and non-ohmic conductor e.g. filament bulb/lamp. For Pure Physics, all the 4 components are needed.

If you consider the composite rod as a whole, the centre of gravity CG is at the pivot. The line of action of the weight which acts from the CG passes through the pivot at P, there is no perpendicular distance, hence no moment created. Thus the rod is balanced at P. But to solve this question, you need to consider the weight of plastic and weight of wood separately in order to find the ratio and apply the Principle of Moments to solve it.

As the reference height is at B, so above that reference height is considered positive, and below the reference height it is considered negative. Hence the height-time graph is as such. Consider a vertical oscillating object, similar to the simple pendulum, the middle is the fastest.

Answer: Option C View the video for explanation

Answer: Option A View the video for explanation