Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

A steel wire of cross-sectional area 0.5mm² is held between two fixed supports. If the wire is just taut at 20^°C, determine the tension when the temperature falls to 0^°C. Coefficient of linear expansion of steel is 1.2 × 10^-5 °C^-1 and its Young's modulus is 2.0 × 10¹¹N m^-2.

Two protons and two electrons are hanging freely at equal distances. Compare the repulsion force between proton and electron.

A particle executes simple harmonic motion. Let P be a point near the mean position and Q be a point near an extreme. The speed of the particle at P is larger than the speed at Q. Still the particle crosses P and Q equal number of times in a given time interval. Does it make you unhappy?

A biconvex lens made of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33. Will the lens behave as a converging or a diverging lens? Give reason.

The dielectric constant decreases if the temperature is increased. Explain this in terms of polarization of the material.

State reason for the generation of displacement current.

A resistance R is connected across a cell of emf ε and internal resistance r. A potentiometer now measures the potential difference between the terminals of the cell as V. Write the expression for 'r' in terms of ε, V and R.

Tell the value and nature of charge on the hole.

If a constant force acts on a particle, its acceleration will:

1. Remain constant.
2. Gradually decrease.
3. Gradually increase.
4. Be undefined.