Figure shows a capacitor made of two circular plates each of radius 12 cm, and separated by 5.0 cm. The capacitor is being charged by an external source (not shown in the figure). The charging current is constant and equal to 0.15 A.

Calculate the capacitance and the rate of charge of potential difference between the plates.
Obtain the displacement current across the plates.
Is Kirchhoff’s first rule (junction rule) valid at each plate of the capacitor? Explain.

An artificial satellite revolves around earth in circular orbit of radius r with time period of orbit T. The satellite is made to stop in the orbit which makes it fall into earth. Time of fall of the satellite onto earth is given by

The I-V graph for a conductor at two different temperatures 100°C and 400°C is as shown in the figure. The temperature coefficient of resistance of the conductor is about (in per degree Celsius)

The I-V graph for a conductor at two different temp. 100°C and 400°C

In a potentiometer experiment, a cell of emf 1.5 V gives a balance point at 75 cm. If the cell is replaced by another cell and the balance point is at 60 cm, the emf of the second cell is:

If the earth shrinks such that its density becomes 8 times to the present value, then the new duration of the day in hours will be

A motor-cyclist moving towards a huge cliff with a speed of 18 kmh^-1, blows a horn of source frequency 325 Hz. If the speed of the sound in air is 330 ms^-1, the number of beats heard by him is

A Carnot engine operates between \( 500 \, \text{K} \) and \( 300 \, \text{K} \). If it absorbs \( 1000 \, \text{J} \) of heat from the source, the amount of work done by the engine is:

Two charges \( +5 \, \mu\text{C} \) and \( +5 \, \mu\text{C} \) are placed 1 m apart. What is the electric potential at the midpoint between them? (Take \(k = 9 \times 10^9 \, \text{N.m}^2/\text{C}^2\)).

A convex lens has a focal length of 20 cm. If an object is placed 30 cm from the lens, what is the image distance?