PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Physics

Two resistors A and B have resistances R_A and R_B, respectively, and R_A < R_B. The resistivities of their materials are ρ_A and ρ_B.

A wire of length 1 m and radius 0.1 mm has a resistance of 100 Ω. Find the resistivity of the material.

A uniform wire of resistance 100 Ω is melted and recast as a wire whose length is double that of the original. What would be the resistance of the wire?

What length of a copper wire of cross-sectional area 0.01 mm² will be needed to prepare a resistance of 1 kΩ? Resistivity of copper = 1.7 × 10^–8 Ωm

A particle of mass 1 g and charge 2.5 × 10⁻⁴ C is released from rest in an electric field of 1.2 × 10 ⁴ N C⁻¹. Find the electric force and the force of gravity acting on this particle. Can one of these forces be neglected in comparison with the other for approximate analysis?

A particle of mass 1 g and charge 2.5 × 10⁻⁴ C is released from rest in an electric field of 1.2 × 10 ⁴ N C⁻¹.   How long will it take for the particle to travel a distance of 40 cm?

A particle of mass 1 g and charge 2.5 × 10⁻⁴ C is released from rest in an electric field of 1.2 × 10 ⁴ N C⁻¹. What will be the speed of the particle after travelling this distance? 

A particle of mass 1 g and charge 2.5 × 10⁻⁴ C is released from rest in an electric field of 1.2 × 10 ⁴ N C⁻¹. How much is the work done by the electric force on the particle during this period?

A ball of mass 100 g and with a charge of 4.9 × 10⁻⁵ C is released from rest in a region where a horizontal electric field of 2.0 × 10⁴ N C⁻¹ exists. (a) Find the resultant force acting on the ball. (b) What will be the path of the ball? (c) Where will the ball be at the end of 2 s?

A block of mass m with a charge q is placed on a smooth horizontal table and is connected to a wall through an unstressed spring of spring constant k, as shown in the figure. A horizontal electric field E, parallel to the spring, is switched on. Find the amplitude of the resulting SHM of the block. 

An electric field of 20 NC⁻¹ exists along the x-axis in space. Calculate the potential difference V_B − V_A where the points A and B are
(a) A = (0, 0); B = (4 m, 2m)
(b) A = (4 m, 2 m); B = (6 m, 5 m)
(c) A = (0, 0); B = (6 m, 5 m)
Do you find any relation between the answers of parts (a), (b) and (c)?  

Consider the situation of the previous problem. A charge of −2.0 × 10⁻⁴ C is moved from point A to point B. Find the change in electrical potential energy U_B − U_A for the cases (a), (b) and (c). 

A capacitor having a capacitance of 100 µF is charged to a potential difference of 24 V. The charging battery is disconnected and the capacitor is connected to another battery of emf 12 V with the positive plate of the capacitor joined with the positive terminal of the battery. (a) Find the charges on the capacitor before and after the reconnection. (b) Find the charge flown through the 12 V battery. (c) Is work done by the battery or is it done on the battery? Find its magnitude. (d) Find the decrease in electrostatic field energy. (e) Find the heat developed during the flow of charge after reconnection.

An electric field  \[\vec{E}  = ( \vec{i} 20 +  \vec{j} 30)   {NC}^{- 1}\]  exists in space. If the potential at the origin is taken to be zero, find the potential at (2 m, 2 m).

The electric potential existing in space is \[\hspace{0.167em} V(x,   y,   z) = A(xy + yz + zx) .\] (a) Write the dimensional formula of A. (b) Find the expression for the electric field. (c) If A is 10 SI units, find the magnitude of the electric field at (1 m, 1 m, 1 m).