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Physics Unit 8 Test

Total questions: 40

Worksheet time: 3600secs

Name
Class
Date
1.

A charged particle with velocity 2×103 m/s passes undeflected through electric and magnetic field intensity. Magnetic field is 1.5 T. The electric field intensity would be

a)

2×103 N/C

b)

1.5×103 N/C

c)

3×103 N/C

d)

4/3×10–3 N/C

2.

An electron of mass m is accelerated through a potential difference of V and then it enters a magnetic field of induction B normal to the lines. Then the radius of the circular path is

a)

2eVm\sqrt[]{\frac{2eV}{m}}  

b)

2VmeB\sqrt[]{\frac{2Vm}{eB}}  

c)

2VmeB2\sqrt[]{\frac{2Vm}{eB^2}}  

d)

2Vme2B\sqrt[]{\frac{2Vm}{e^2B}}  

3.

Two current carrying conductors are placed parallel as shown in figure. Which point will experience the strong magnetic field?

a)

X

b)

Both experience same magnetic field

c)

Y

d)

None of these

4.

The acceleration of an electron of mass m and charge e, moving with uniform speed v at right angles to a magnetic field of flux density B, is give by

a)

Bevm\frac{Bev}{m}  

b)

Bem\frac{Be}{m}  

c)

Bvm\frac{Bv}{m}  

d)

BevmBevm  

5.

The radius of curvature of the path of the charged particle in a uniform magnetic field is directly proportional to

a)

The energy of the particle

b)

The intensity of the field

c)

The momentum of the particle

d)

The charge on the particle

6.

Direction of magnetic flux is

a)

Normal to the surface

b)

Parallel to the surface

c)

At any angle

d)

No direction

7.

In step up transformer, voltage in the secondary increases and power in secondary

a)

Remain same

b)

Increases because current decreases

c)

Decreases because voltage increases

d)

May increases if voltage remain same

8.

The magnetic flux linked with a coil is changed from 1 weber to 0.1 weber in 0.1 sec. the induced e.m.f is:

a)

9V

b)

0.009V

c)

10V

d)

1/9V

9.

Laminated core in a transformer is used to reduce

a)

Eddy current losses

b)

Hysteresis losses

c)

Iron losses

d)

Heat losses due to resistance

10.

A transformer steps 220 V to 40 voltages. If the secondary turns are 40 and primary turns are:

a)

20

b)

40

c)

120

d)

220

11.

During one cycle, the direction of flow of alternating current

a)

Changes once

b)

Changes twice

c)

Remains same

d)

Not changes in magnitude

12.

In a step up transformer the turn ratio is 1:2. A Lechlanche cell (emf = 1.5 V) is connected across the primary. The voltage across the secondary is:

a)

3 V

b)

0.75 V

c)

1.5 V

d)

Zero

13.

The maximum value of induced emf in a coil rotating in magnetic field does not depend on

a)

The resistance of coil

b)

The number of turns in the coil

c)

The area of the coil

d)

Rotational frequency of the coil

14.

The north pole of a long horizontal bar magnet is being brought closer to a vertical conducting plane along the perpendicular direction. The direction of the induced current in the conducting plane will be

a)

Horizontal

b)

Vertical

c)

Clockwise

d)

Anticlockwise

15.

The armature of a generator consists of a flat square coil of side 4 cm and 200 turns. The coil rotates in a magnetic field of 0.75T. The angular speed so that a maximum emf of 1.6V is generated is           

a)

203rads−1\frac{20}{3}rads^{-1}  

b)

203\frac{20}{3} rotations/s

c)

203\frac{20}{3} rpm 

d)

None

16.

An electron moving east is acted on by a magnetic field in the north direction. The force on the electron is:

a)

Vertically upwards

b)

Towards north

c)

Vertically downwards

d)

Towards east

17.

Two charges are projected in a magnetic field. Their paths after entering field is shown in figure. What type of these charges are?

a)

One is proton and other is α-particle

b)

One is proton and other is neutron

c)

One is electron and other is proton

d)

None of these

18.

A wire of length 2 m carries a current of 10 A. What is the force acting on it when it is placed at an angle of 45° to the uniform magnetic field of 0.15 T?

a)

1.2 N

b)

3.2 N

c)

2.5 N

d)

32N\frac{3}{\sqrt[]{2}}N  

19.

A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. The frequency taken by the particle to complete one revolution is

a)

2πmqB\frac{2\pi m}{qB}  

b)

2πq2Bm\frac{2\pi q^2B}{m}  

c)

qB2πm\frac{qB}{2\pi m}  

d)

2πmqB\frac{2\pi mq}{B}  

20.

The ability of a material to conduct magnetic flux through it.

a)

Permittivity

b)

Reluctivity

c)

Conductivity

d)

Permeability

21.

An electron and a proton with equal momentum enter perpendicularly into a uniform magnetic field, then

a)

The path of proton shall be more curved than that of electron

b)

The path of proton shall be less curved than that of electron

c)

Both are equally curved

d)

Path of both will be straight line

22.

Lenz's law gives

a)

The magnitude of the induced e.m.f

b)

Both the magnitude and direction of the induced current

c)

The direction of the induced current

d)

The magnitude of the induced current

23.

According to Flemming’s left-hand rule, the index finger denotes?

a)

Direction of magnetic field

b)

Direction of current

c)

Direction of force

d)

Direction of force as well as current

24.

When a bar magnet is broken into two pieces, which of the following are true?

a)

The magnet loses its magnetism

b)

The magnet has only north pole left

c)

The magnet has only south pole left

d)

The magnet turns into two new bar magnets

25.

When a wire loop is rotated in a magnetic field, the direction of induced emf changes in every

a)

1 revolution

b)

1/2 revolution

c)

1/4 revolution

d)

2 revolution

26.

If the supply frequency (f) of a transformer decrease, the effect of frequency on the transformer's secondary output voltage?

a)

Decreases

b)

Increases

c)

All of these

d)

Remain same

27.

An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true?

a)

Trajectory of electron is less curved

b)

Trajectory of proton is less curved

c)

Both trajectories are equally curved

d)

Both move on straight line path

28.

A power station generates 600 MW of electrical power which is fed to a transmission line. If the input voltage is 300 KV, then what current would flow in the transmission line?

a)

5 × 103 A

b)

10 × 103 A

c)

2 × 103 A

d)

7 × 103 A

29.

A circular loop of area 200 cm2 lies in x-z plane, then a uniform magnetic field B = (0.3i + 0.4j) is applied on it, find the magnetic flux through the loop:

a)

0.8 wb

b)

8 wb

c)

0.008 wb

d)

0.08 wb

30.

A coil having 500 square loops each of side 10 cm is placed normal to a magnetic field which increases at a rate of 1T/s. The induced emf in volts is:

a)

0.1

b)

0.5

c)

1

d)

5

31.

An electron is moving in circle of radius r in a uniform magnetic field B. Suddenly the field is reduced to B/2 The radius of the circle now becomes

a)

r/2

b)

2r

c)

r/4

d)

4r

32.

A loop of radius 1 m is place on a inclined of 60 degree with the magnetic field of 100 T, corresponding flux will be

a)

314 Wb

b)

107 Wb

c)

157 Wb

d)

435 Wb

33.

Eddy currents produced in the core of transformer are responsible for

a)

Heat loss

b)

Step-down process

c)

Step-up process

d)

Induction phenomenon

34.

Steady current I flows through a wire. A circular loop of wire is placed next to the wire. Which of the following will produce an induced current in the loop?

a)

Move the loop away from wire

b)

Increase the electric current in wire

c)

Decrease the electric current in wire

d)

All of these

35.

A bar magnet is hung by a string with North Pole faced downward starts oscillating above a horizontal circular coil. Which of the following statement about the induced current is true (viewed from above).

a)

Induced current flows clockwise

b)

Induced current flows anticlockwise

c)

Induced current reverses it direction repeatedly

d)

None of these

36.

A generator produces a voltage that is given by V=230 sin 314 t volt, where time “t” is in second. The frequency of this voltage is:

a)

55 Hz

b)

19 Hz

c)

60 Hz

d)

50 Hz

37.

A copper ring having a cut such as not to form a complete loop is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet is:

a)

g

b)

More than g

c)

Less than g

d)

Depends on the relative size of the cut

38.

Which quantity is decreased in an ideal step-down transformer?

a)

Current

b)

Power

c)

Voltage

d)

Frequency

39.

For an efficient transformer, the hysteresis loop for its core is ___ in size:

a)

Infinite

b)

Zero

c)

Smaller

d)

Larger

40.

Out of following, what is true for a transformer?

a)

Coils are electrically connected

b)

Coils are electrically & magnetically insulated

c)

Coils are magnetically insulated

d)

Coils are electrically insulated but magnetically connected

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