Download App

Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsElectrostatic Potential and Capacitance5 Marks
Question
An electrical technician requires a capacitance of 2μF in a circuitacross a potential difference of 1kV. A large number of 1μF capacitors are available to him each of which can withstand a potential difference of not more than 400V. Suggest a possible arrangement that requires the minimum number of capacitors.
✓

Answer

Total required capacitance, C = 2μF Potential difference, V = 1kV = 1000V Capacitance of each capacitor, C1 = 1μF

Each capacitor can withstand a potential difference, V1 = 400V

$\frac{1000}{400}={2.5}$

Suppose a number of capacitors are connected in series and these series circuits are connected in parallel (row) to each other. The potential difference across each row must be 1000V and potential difference across each capacitor must be 400V. Hence, number of capacitors in each row is given as,

Hence, there are three capacitors in each row.

Capacitance of each row $=\frac{1}{1+1+1}=\frac{1}{3}\ \mu \text{F}\ \frac{1}{3}+\frac{1}{3}+\frac{1}{3}+ .....\text{n terms,}$ 

However, capacitance of the ciruit is given as 2μF.

$\therefore\ \frac{\text{n}}{3}={2}$

N = 6

Let there are n rows, each having three capacitors, which are connected in parallel. Hence,equivalent capacitance of the circuit is given as,

Hence, 6 rows of three capacitors are present in the circuit. A minimum of 6 × 3 i.e., 18capacitors are required for the given arrangement.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Long Answer Type Questions [5M]" from Electrostatic Potential and Capacitance→Electrostatic Potential and Capacitance — all question types→Physics STD 12 Science question papers→Bihar Board STD 12 Science question papers→Bihar Board question paper generator→

Similar questions

Two identical pith balls are charged by rubbing against each other. They are suspended from a horizontal rod through two strings of length 20cm each, the separation between the suspension points being 5cm. In equilibrium, the separation between the balls is 3cm. Find the mass of each ball and the tension in the strings. The charge on each ball has a magnitude 2.0 × 10-8C.
→
A point source emitting alpha particles is placed at a distance of 1m from a counter which records any alpha particle falling on its 1cm2 window. If the source contains 6.0 × 1016 active nuclei and the counter records a rate of 50000 counts/ second, find the decay constant. Assume that the source emits alpha particles uniformly in all directions and the alpha particles fall nearly normally on the window.
→
What is transformer ? Describe its construction and working principle.
→
A magnetic field in a certain region is given by $\text{B}=\text{B}_0\cos(\omega\text{t})\hat{\text{k}}$ and a coil of radius a with resistance R is placed in the x-y plane with its centre at the origin in the magnetic field (see Fig). Find the magnitude and the direction of the current at (a, 0, 0) at $\text{t}=\frac{\pi}{2\omega},\text{t}=\frac{\pi}{\omega} \text{ and }\text{t}=\frac{3\pi}{2\omega}$.

→
A compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at (a) the least distance of distinct vision (25 cm), and (b) at infinity? What is the magnifying power of the microscope in each case?
→
Write Faraday's laws of electromagnetic induction and derive them.
→
The current in an ideal, long solenoid is varied at a uniform rate of 0.01A/s. The solenoid has 2000 turns/m and its radius is 6.0cm.
  1. Consider a circle of radius 1.0cm inside the solenoid with its axis coinciding with the axis of the solenoid. Write the change in the magnetic flux through this circle in 2.0 seconds.
  2. Find the electric field induced at a point on the circumference of the circle.
  3. Find the electric field induced at a point outside the solenoid at a distance 8.0cm from its axis.
→
Find the expression for the energy stored in the capacitor. Also find the energy lost when the charged capacitor is disconnected from the source and connected in parallel with the uncharged capacitor. Where does this loss of energy appear?
→
A block of mass m slips on a rough horizontal table under the action of a horizontal force applied to it. The coefficient of friction between the block and the table is $\mu.$ The table does not move on the floor. Find the total frictional force applied by the floor on the legs of the table. Do you need the friction coefficient between the table and the floor or the mass of the table?
→
A wire of length l is bent in the form of an equilateral triangle and carries an electric currrent i.
  1. Find the magnetic field B at the centre.
  2. If the wire is bent in the form of a square, what would be the value of B at the centre?
→