CBSE Guess > Papers > Important Questions > Class XII > 2007 > Physics > Physics (Magnetism And Magnetic Effect Of Current) By: Mr. Abhishek Gupta

Magnetism And Magnetic Effect Of Current

Q. 1. Define Coulomb. Calculate the charge carried by 12.5 x 10¹⁸ electrons.

Q. 2. Define resistivity of a material. Does it depend on temp?

Q. 3. How many protons will have the total charge of 1C

Q. 4. Find the current drawn when a battery of emf E and internal resistance r is connected across an external resistance R

Q. 5. State Faraday’s laws of electrolysis. Define electrochemical equivalent

Q. 6. An electron travels in a circular path of radius 20cm in a magnetic field of 2mT. Calculate the speed of the electron. What is the potential difference through which the electron must be accelerated to acquire this speed?

Q. 7. Explain how you will convert a galvanometer into a voltmeter of a given range

Q. 8. State Gauss’s law in electrostatics. Apply this to show that for a spherical shell, the electric field inside the shell vanishes whereas outside it, the field is as if all the charge had been concentrated at the center.

Q. 9. State the 2 Kirchoff law

Q. 10. Show that in a uniform electric field, a dipole experiences only a torque but no net force. Derive expression for the torque.

Q. 11. An electron moving with a velocity of 10⁸m/s enters a magnetic field of 50G in a direction perpendicular to it. Calculate

1. Radius of the path and
2. Frequency of revolution

Q. 12. Define Capacitance. Show that the energy density in a parallel plate capacitor is ½ЄoE²

Q. 13. Why 2 electric field lines do not intersect?

Q. 14. Define magnetic moment of a dipole and give its SI unit.

Q. 15. How does the velocity of a charged particle affect its

1. Mass
2. Charge

Q. 16. Explain Seebeck effect. What is the use of the Seebeck series?

Q. 17. State one main difference b/w primary and secondary cells.

Q. 18. An oil drop of weight 3.2 x 10^-14Kg is balanced in an electric field of 5x10⁵ V/m, find the charge on the oil drop.

Q. 19. The sequence of bands marked on a carbon resistor are Yellow, Red, Orange and silver. Find the resistance and the tolerance

Q. 20. The coil of a galvanometer has a resistance of 100ohm. It shows full scale deflection for a current of 0.5mA. How will you convert it into a voltmeter to read a potential difference of 5Volts.

Q. 21. Find the magnetic moment associated with a coil of 10 turns, area 10^-4m² and carrying a current of 2A

Q. 22. The work done in moving a charge of 3C from A to B is 6J. Find the potential difference b/w A and B

Q. 23. A dry cell of EMF 1.5 volts and internal resistance 0.1ohm if connected to a resistor R. If the current drawn from the cell if 2A, find the voltage drop across R and power dissipated in it.

Q. 24. Derive the expression for the torque on a rectangular coil of area A carrying current I placed in a magnetic field B. The angle b/w direction of B and the area vector of the coil is θ.

Q. 25. What is a dielectric? A dielectric slab of thickness t is placed b/w the plates of a parallel plate capacitor having plate separation d and plate area A. Derive the capacitance.

Q. 26. Find the electric field b/w 2 metal plates 5mm apart, connected by a 12V battery.

Q. 27. Write an expression connecting the thermo-electric emf with temp difference.

Q. 28. Give the colour sequence for a 47Kohm resistor.

Q. 29. Write two special characteristics of the wire of an electric heater.

Q. 30. A metallic wire of length 1m is stretched to double its length. Calculate the ratio of initial to final resistance.

Q. 31. Explain

1. An ammeter is a low resistance device and it is always connected in series
2. A good voltmeter should have high resistance and it is always connected in parallel

Q. 32. Name 2 materials which are used for making standard resistance coils. Why are these materials preferred over others?

Q. 33. When a potentiometer is connected b/w A and B the balance length is 300cm. On connecting the potentiometer A B C across A and C, the balance length is 100cm. Find E₁/E₂

Q. 34. Find the magnetic field at the center of the circular loop shown here 10A

Q. 35. Define angle of dip. What is the angle of dip at

1. Poles
2. Equator

Q. 36. A charge of 12C is given to a hollow sphere of radius 0.1m. Find the potential at the surface and at the centre of the sphere.

Q. 37. A battery of emf 3 volts and internal resistance r is connected in series with a resistor of 55ohm through an ammeter of 1Ω. The ammeter reads 50mA. Draw the circuit diagram and calculate the value of r.

Q. 38. With the help of a suitable diagram, explain the construction and working of a dry cell.

Q. 39. A set of n identical resistors each of resistance R, when connected in series give a net of X ohm and when connected in parallel give a net of Y ohm. Show that XY=R²

Q. 40. A long straight wire carries a current of 3A. Calculate the magnitude of magnetic field at a distance of 10cm from the wire. Draw a diagram to show that a current carrying wire has no poles.

Q. 41. A beam of electrons passes undeflected through a region of mutually perpendicular E and B. If the electric field is cut-off, the electron beam moves in a circular path of radius R. Derive an expression for the e/m ratio of the electron in terms of E, B and R.

Q. 42. Give 2 factors on which thermo-electric emf depends

Q. 43. Two point electric charges A and B of unknown magnitude and sign are placed d distance apart. The electric field is zero at a point, not b/w the charges but on the line joining them and closer to A. Write 2 essential conditions for this to happen

Q. 44. Define sensitivity of a potentiometer. How can it be increased.

Q. 45. Mention 2 disadvantages & 2 uses of the cyclotron