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Question Bank No: 3

1. A line having a total resistance of 0.2 ohm delivers 10kW at 220V to a small factory. The efficiency of transmission is

a)		0.96
b)		1
c)		0.9
d)		0.22

2. A 6V storage battery is being charged at the rate of 20 C/s. The power used to charge the battery is

a)		12W
b)		120W
c)		1200W
d)		20W

3. In an electrolysis, 5A of current is used for a certain time and 0.5 mol of silver is deposited, If the current is doubled and time is also doubled, the amount of silver deposited in 'mol' is

a)		2 mol
b)		1 mol
c)		3 mol
d)		4 mol

4. The amount of charge in coulombs required to deposit one gram equivalent of substance by electrolysis is

a)		6.023 x 10 23
b)		6 x 10 24
c)		1.6 x 10-19
d)		96500

5. A proton and $α$ -particle are prjected with same kinetic energy at right angles to a uniform magnetic field. Which statement is correct?

a)		$α$ - particle bends in a circular path with smaller radius
b)		$α$ - particle bends in a circular path of greater radius
c)		Radii of both the particles are the same
d)		Both will move in stright line

6. A wire of length 2m carries a current of 10A. What is the force acting on it when it is placed at angle of $45^{0}$ to a uniform magnetic field of 0.15T?

a)		1.5N
b)		3N
c)		$\sqrt{3} / 2 N$
d)		$3 / \sqrt{2} N$

7. Electrons moving at right angles of a uniform magnetic field completes a circular orbit in $10^{- 9}$ seconds. If $m = 9 \times 10^{- 31}$ kg and $e = 1.6 \times 10^{- 19}$ C; the uniform field is

a)		$3.53 \times 10^{- 2} T$
b)		$3.53 \times 10^{- 1} T$
c)		$7.06 \times 10^{- 2} T$
d)		zero

8. A uniform electric field and uniform magnetic field are produced in the same direction. An electron is projected with an initial velocity in the same direction. Then the electron

a)		turns to the left
b)		turns to the right
c)		has its velocity increased
d)		has its velocity decreased

9. A horizontal wire of mass $3 \times 10^{- 3}$ kg and length of 2m carry a current of 9.8A. It is kept in a vertical magnetic field. What is the magnetic of the field which can support the wire?

a)		$1.5 \times 10^{- 3} T$
b)		$3 \times 10^{- 3} T$
c)		$3 / 9.8 \times 10^{- 3} T$
d)

10. A circular loop of radius 'r' carries a steady current produces a magnetic field of 2T at its center. If the radius of the loop is decreased one fourth and the current is increased twice, then the magnetic field at its center becomes

a)		2T
b)		8T
c)		16T
d)		32T

11. The mutual force of repulsion between two long and parallel wires in air is 'F', when they carry a certain current. If the current is doubled and the distance between them is tripled, the new force will be

a)		2/9 F
b)		4/9 F
c)		2/3 F
d)		4/3 F

12. A galvenometer has a rectangular coil area $10^{- 3} m 3$ and having 200 turns. If the coil is placed in a uniform magnetic field of 0.5T and the restoring torque per unit twist is $10^{- 16}$ Nm per degree, the maximum current measured by it, if its coil turns through $45^{0}$ for full scale deflection

a)		$4.5 \times 10^{- 8} A$
b)		$45 \times 10^{- 4} A$
c)		$0.45 \times 10^{- 8} A$
d)		$4.5 \times 10^{- 4} A$

13. When a shunt resistance of 5 ohm is connected to a galvanometer, its deflection decreases from 5 division to 1 division. Then the resistance of the galvanometer is

a)		10 ohm
b)		15 ohm
c)		20 ohm
d)		25 ohm

14. A proton and deutron accelearated through the same potential enter a uniform magnetic field in a direction at right angles to it. Then the ratio of radii of path of proton to deutron is

a)		1: $\sqrt{2}$
b)		2:1
c)		$\sqrt{2}$ :1
d)		1:2

15. Two identical cells each of emf 1.5V are first connected in series to a resistance, and found that a current 1A is flowing through it. The two cells are connected in parallel and then to the same resistance. If a current of 0.5A is flowing through the resistance, the internal resistance of the cell is

a)		1 ohm
b)		0.5 ohm
c)		1.5 ohm
d)		zero

16. A 50W 200V electric bulb is connected in series with a room heater of 200 ohm the combination is then connected to 200V. Then it is replaced by a 100W, 200V bulbs. Then the ratio of the power dissipated by the room heater in the two cases is

a)		3/5
b)		2/5
c)		5/3
d)		5/2

17. A galvanometer has a resistance of 55 ohms. It gives full scale deflection by current of 10 milli amperes. The resistance that has to be connected across it to enable it to read 1 ampere current is

a)		5.55 ohms
b)		0.555 ohms
c)		55.5 ohms
d)		0.0555 ohms

18. Two very long parallel wires carrying 2A and 3A current in the opposite direction are at a distance of 10cm from each other in air. Then the force exerted by one another per meter in newtons is

a)		$1.2 \times 10^{- 6}$ repulsion
b)		$1.2 \times 10^{- 5}$ attraction
c)		$0.12 \times 10^{- 6}$ attraction
d)		$1.2 \times 10^{- 5}$ repulsion

19. Two identical circular coils are kept with their planes at right angles and cneters coinciding. If the same current is passing through the coil, the magnitude of the resultant magnetic field at the center is

a)		2 times that due to one coil
b)		2 $\sqrt{2}$ times that due to one coil
c)		1/2 of that due to one coil
d)		$\sqrt{2}$ times that due to one coil

20. A toroid of radius 0.05m and total number of turns 1000, carries a current 0f 2A. Then the magnetic field at a point on its axis is

a)		$8 \times 10^{- 3} T$
b)		$4 \times 10^{- 3} T$
c)		$2 \times 10^{- 3} T$
d)		zero

21. A galvanometer having a resistance of 20 ohms reads 1mA per division. When a shunt of 2 ohms is connected across i, one division is corresponding to

a)		11 mA
b)		1.1 mA
c)		22 mA
d)		2.2 mA

22. A particle carrying a charge equal to charge on an electron is rotating 100 times per second in a circular path of radius 0.8m the value of magnetic field produced at the center will be

a)		$10^{- 7} μ_{0}$
b)		$10^{- 17} μ_{0}$
c)		$10^{- 6} μ_{0}$
d)		$10^{7} μ_{0}$

23. The lines of force around an infinite straight conductor carrying a current in each conductor is doubled then the value of force will be

a)		concentric circles
b)		parallel to the conducter
c)		perpendicular to the conductor
d)		elliptical

24. The force existing between two current carrying conductors in F. If the current in each conductor is doubled the the value of force will be

a)		4F
b)		3F
c)		2F
d)		F

25. A galvanometer has a resistance of 5 ohm and a full scale deflection is produced by 15mA. The resistance required to read 1.5V is

a)		$9 \times 10^{- 3} Ω$
b)		$9 \times 10^{+ 3} Ω$
c)		$0.95 Ω$
d)		$95 Ω$

26. A cyclotron in which the magnetic field is 1.4 T is used to accelerate protons. How rapidly should the electric field between the dees be reversed?

a)		$2.343 \times 10^{- 8} s$
b)		$2.343 \times 10^{- 7} s$
c)		$2.343 \times 10^{- 6} s$
d)		$2.343 \times 10^{- 9} s$

27. A straight horizontal conducting rod of length 0.5m and 0.1 kg is suspended by two vertical wires at its ends. A current of 10A flows through the rod. The magnetic field set up normal to the wire so that the tension in the wire is zero is

a)		1.96T
b)		0.196T
c)		$1.96 \times 10^{3} T$
d)		19.6 T

28. An electron beam is deflected in a given field. The nature of this uniform field can be obtained as

a)		axial magnetic field if path is circular
b)		transverse electric field if path is straight line
c)		electric if path is parabola and magnetic if path is circular
d)		magnetic if path of beam is parabola

29. A given cyclotrone can be used to produce high energy in

a)		$α$ -particles
b)		$β$ -particles
c)		$γ$ - rays
d)		hydrogen atom

30. In moving coil galvanometer the deflection of the coil is related to electric current as

a)		i $α$ tanQ
b)		i $α Q$
c)		$z α \sqrt{Q}$
d)		$2 α Q^{2}$