Download 12th Physics

HOLIDAY HOMEWORK PHYSICS 12TH
1. A Parallel plate capacitor with air between the plates has a capacitance of 8pF.What will be the capacitance if
the distance between the plates be reduced by half and space between them is filled with a substance of
dielectric constant K=6? (Ans: 96pF)
2. Two point charges 4µC and -2µC are separated by a distance of 1 metre in air. At what point on the line joining
the charges is the electric potential zero? (Ans: 0.33m)
3. An Electric dipole of length 4cm, when placed with its axis making an angle of 60⁰ with a uniform electric field
experiences a torque of 4√2 Nm. Calculate(i) magnitude of the electric field.(ii) potential energy of dipole, if
dipole has charges of ±8 nC. (Ans: 2.5 X 𝟏𝟎𝟏𝟎 N𝑪−𝟏 ; 4J)
4. Three capacitors of capacitances 2pF, 3pf and 4pF are connected in parallel. (a)What are the total capacitances
of the capacitances of capacitor? (b)Determine charge on each capacitor if combination is connected to 100V
supply. (Ans: 9pF; 2X𝟏𝟎−𝟏𝟎 C, 3X𝟏𝟎−𝟏𝟎 C, 4X𝟏𝟎−𝟏𝟎 C)
5. A 12pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor? (Ans:
1.5 X 𝟏𝟎−𝟖 J).
6. Calculate the amount of work done to dissociate a system of three charges 1µC, 1µC and 4µC placed on the
vertices of an equilateral triangle of side 10 cm. (Ans: 0.63J)
7. A 600pF capacitor is charged by a 200V supply. It is then disconnected from the supply and is connected to
another uncharged 600pF capacitor. How much electrostatic energy is lost in the process? (Ans: 6 X 𝟏𝟎−𝟔 J)
8. In a parallel plate capacitor with air between the plates, each plate has an area 6 X 10−3 m2 and distance
between plates is 3mm. Calculate the capacitance of capacitor. If this capacitor is connected to 100V supply,
what is the charge on each plate of capacitor?
(Ans: 17.7pF; 1.8nC)
9. A parallel plate capacitor has its two plates kept 0.02m apart. A dielectric slab of thickness 0.01m is introduced
between the plates with its faces parallel to them. The distance between the plates is readjusted to make the
capacity of the capacitor 2/3rd of its original value. Given that dielectric constant of slab equals 5, find new
distances between the plates. (Ans=0.38m).
10. Two point charges 2µC and +6µC repel each other with a force of 12N. In each is given the additional
charge -4µC, what will be the new force between them? (Ans: 4N)
11. A parallel plate capacitor each with plate area A and separation‘d’ is charged to a potential difference V. The
battery used to charge it is then disconnected. A dielectric slab of thickness‘d’ and dielectric constant K is now
placed between the plates. What charge if any, will take place in:(i)
Charge on the plates
(ii)
Electric field intensity between the plates
(iii)
Capacitance of the capacitor
Justify your answer in each case.
12. Calculate the amount of work done in rotating a dipole of dipole moment 3x10-8 cm, from its
position of stable equilibrium to the position of unstable equilibrium, in a uniform electric
field of intensity 104 N/C.
13. The two plates of parallel plate capacitor are 4mm apart. A slab of dielectric constant 3 and
thickness 3mm is introduced between the plates with its faces parallel to them. The distance
between the plates is so adjusted that the capacitance of the capacitor becomes 2/3 rd of its
original value. What is the new distance between the plates?
14. Find the charge on the
Capacitor as shown in the circuit.
15. Net capacitance of three identical capacitors in series is 1µF. What will be their net capacitance if
connected in parallel? Find the ratio of energy stored in the two configurations if they are both
connected to the same source.
16. Two capacitors of capacitance 6µF and 12 µF are connected in series with a battery. The voltage
across the 6µF capacitor is 2V. Compute the total battery voltage.
17. A network of four capacitor each of 15µF capacitance to a 500V
supply as shown in the figure. Determine
(i) Equivalent capacitance of the network
(ii) Charge on each capacitor.
18. A 4µF capacitor is charged by a 200 V supply. It is then
disconnected from the supply and is connected to another uncharged 2µF capacitor. How much
electrostatic energy of the first capacitor is lost in the form of heat and electrostatic radiation?
 DO REVISION OF UNIT 1 AND 2