Magnets and Magnetic Fields Generix Content - Magnets and Magnetic Fields
"Magnets and Magnetic Fields" question number distribution across years
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JAMB questions for "Physics :: Magnets and Magnetic Fields"
Q1
In the diagram beside, if the magnetic field points into the paper and the force on a current-carrying conductor points upwards, what is the direction of the current?
A
Right
B
Left
C
Downwards
D
Upwards
E
Q2

Which of the following diagrams represents the magnetic field of two isolated unlike poles?

A
B
C
D
E
Q3

A proton moving with a speed of 1.0 x 106 ms-1 through a magnetic field of 1.0 T experiences a magnetic force of magnetic 8.0 x 10-14 N. The angle between the proton's velocity and the field is

A

45°

B

30°

C

60°

D

90°

E
Q4
The north pole of a magnet can never be separated from the south pole because of a property known as
A
magnetic dipole
B
magnetic octopole
C
magnetic monopole
D
E
Q5
Two charged particles are projected into a region where there is a magnetic field perpendicular to their velocities. If the charges are deflected in  opposite directions, which of the following statements is true of the charges?
A
The charges are of the same sign
B
Positive charge are more in number
C
The charges must be of opposite sign
D
The charges are electrically neutral
E
Q6
To protect a material from the influence of an external magnetic field, the material should be kept in a
A
square steel ring
B
triangular zinc ring
C
soft iron ring
D
loop of copper wire
E
Q7
I. It retains its magnetism much longer than steel II. It is more easily magnitized than steel III. It is more easily demagnetized than steel IV. It produces a stronger magnet than steel Which combination of the above makes iron preferable of steel in the making of electromagnets?
A
II, III and IV only
B
I, III and IV only
C
I and II  only
D
II and III only
E
Q8
A magnetic field is said to exist at a point if a force is
A
deflected at the point
B
strengthened at the point
C
exerted on a moving charge at the point
D
exerted on a stationary charge at the point
E
Q9
The force on a charge moving with velocity v in a magnetic field B is half of the maximum force when the angle between v and B is
A
B
90°
C
45°
D
30°
E
Q10
The electromagnetic wave that can produce a heating effect on the environment is
A
gamma ray
B
infrared rays
C
x- rays
D
ultraviolet rays
E
Q11
What is the angle of dip at the magnetic equator?
A
180°
B
90°
C
45°
D
E
Q12
The magnetic force on a charged particle moving with velocity v is
A
proportional to the magnitude of the charge only
B
proportional to the velocity v only
C
independent of the magnitude of the charge
D
proportional to both the magnitude of the charge and the velocity v.
E
Q13
The force on a current carrying conductor in a magnetic field is greatest when the
A
conductor is parallel with the field
B
conductor makes an angle of 60° with the field
C
conductor is at right angles with the filed.
D
force is independent of the angle between the field and the conductor
E
Q14
If a charged ion goes through combined electric and magnetic fields, the resultant emergent velocity of the ion is
A
E/B
B
EB
C
B/E
D
E-B
E
Q15
A conductor of length 2m carries a current of 0.8 A while kept in a magnetic field of magnetic flux density 0.5 T. The maximum force acting on it is
A
8.0 N
B
3.2 N
C
0.8 N
D
0.2 N
E
Q16
Which of the following electromagnetic waves is least energetic?
A
infra-red rays
B
X-rays
C
Ultra -violet rays
D
Gamma rays
E
Q17
Steel is more suitable for permanent magnet than iron because the former
A
is easily demagnetized by shaking vigorously
B
is an alloy of many metals
C
is easily magnetized by alternating current through one cycle
D
retains magnetism more than iron
E
Q18

The diagram below represents a transverse electromagnetic wave travelling with speed 3.0 X 108 ms-1. What is the frequency of the wave?

A

3.0 X 107 Hz

B

9.0 X 107 Hz

C

1.0 X 10Hz

D

3.0 X 10Hz

E
Q19
The diagram below shows a magnet X with its South pole moved along a soft iron bar PQ in the direction shown. After some time, the poles at P and Q respectively are
A
North-North
B
North-South
C
South-North
D
South-South
E
Q20

The force of repulsion between two point positive charges 5 μC and 8 μC separated at a distance of 0.02 m apart is [1/4Εo  = 9 x 109  NM C-2 ]

A

1.8 X 10-10 N

B

9.0 X 10-8  N

C

9.0 x 102 N

D

4.5 x 103 N

E
Q21
An ebonite rod rubbed with fur attracts a glass rod rubbed with silk because
A
ebonite has a negative charge while glass has a positive charge
B
ebonite has a positive charge while glass has a negative charge
C
both have negative charges
D
both have positive charges
E
Q22

Which of the following diagrams shows the correct direction of the magnetic lines of force of a vertical wire XY carrying a current I?

A
B
C
D
E
Q23
The electromagnetic waves that are sensitive to temperature changes are
A
x- rays
B
gamma-rays
C
ultra-violet rays
D
infra-red rays
E
Q24
At different locations on the earth's surface, the earth's magnetic field is
A
the same in magnitude and direction
B
the same in magnitude but different in direction
C
different in both magnitude and direction
D
different in magnitude but not in direction
E
Q25
When a biro pen rubbed on a dry silk cloth is moved very close to a piece of paper on a dry table, the pen is found to pick up the paper. This is because
A
both the pen and the cloth are magnetized
B
the pen is magnetized but the cloth is not
C
the pen is charged while the cloth is magnetized
D
both the pen and the cloth are charged
E
Q26
The field that results from the contact of a positively charged ball with the inner wall of an unchanged hollow conducting sphere is
A
inside the sphere
B
on the surface of the ball
C
inside and outside the sphere
D
outside the sphere
E
Q27
Which of the following correctly explain(s) why sof iron is preferred to steel in electromagnets?  I.  Soft iron is more readily magnetized than steel  II. Soft iron is more readily demagnetized than steel  III. Soft iron retains magnetism more than steel
A
I only
B
II and III only
C
I and II only
D
I, II and III
E
Q28
A current-carrying conductor experiences a force when placed in a magnetic field because the
A
Conductor is Magnetized
B
Magnetic field of the current interacts with external magnetic field
C
force is due to the motor principle
D
electric field of the current interacts with the external magnetic field.
E
Q29

A horizontal component of the earth's magnetic field and the magnetic field of a straight wire X carries current into the plane of a paper. Which of the following figures correctly illustrates the resultant magnetic field pattern in the horizontal plane?

A
B
C
D
E
Q30
Which of the following arrangements of the components of electromagnetic spectrum is in ascending order to wavelengths?
A
Gamma rays, ultraviolet rays, x-rays, infra red ray
B
Gamma rays, x-rays, ultraviolet rays, infra red rays
C
Infra red rays, ultraviolet rays, x-rays, gamma rays
D
Gamma rays, ultra-violet rays, infra-red rays, x-rays
E
Q31
The angle between the direction of the earth's magnetic field and the horizontal is called the
A
angle of deviation
B
magnetic declination
C
magnetic meridian
D
angle of dip
E
Q32
The diagram below represents the field pattern obtained by bringing the poles of two magnets near each other. The poles must be
A
N-N poles
B
S-S poles
C
S-N poles
D
N-S poles
E
Q33
Which of the following statements is CORRECT about the earth's magnetic field?
A
The angle of dip is the angle which freely suspended magnet makes with the vertical
B
The angle of declination is the angle between the magnetic meridian and the geographic meridian
C
The angle of declination is the angle which a magnetic compass makes with the magnetic meridian
D
The angle of inclination is the difference between the angle of dip and the angle of declination
E
Q34
One of the properties of the earth's magnetic field is that the
A
A north pole lies in the northern hemisphere
B
geographic and magnetic meridians coincide
C
earth's magnetic flux is entirely horizontal at a place where the magnetic dip is zero.
D
earth's magnetic flux is entirely vertical at a place where the magnetic dip is zero
E
Q35
When a number of identical small magnets are arranged in a line, the strength of the resultant magnet
A
is largest when they are arranged and to end
B
is greatest when they area arranged parallel with like poles adjacent to each other
C
depends only on the number of magnets provided they are parralel
D
is greater when the magnets are arranged on a wooden surface than on a metal surface
E
Q36
A bar magnet is most efficiently demagnetized by
A
placing it in a N-5 position and hitting it with a hammer
B
subjecting it to an electric current from a battery
C
bringing it north pole in contact with the north pole of a very strong magnet
D
heating the magnet
E
Q37
The figure beside shows a conductor PQ carrying a current I in the direction shown. At a particular position near the conduct is a compass needle K. Neglecting the earth's magnetic field, the compass needle will
A
settle in any direction
B
settle in a fixed direction only if conductor PQ is a magnetic material
C
settle in a fixed direction whether conductor PQ is a magnetic material or not
D
be stationary
E
Q38
the wore X in the figure beside is at right angles tot he plane of the paper and carries a current into the paper. At which of the points labelled 1-4 will the magnetic flux density die to this current in the same direction as that of the horizontal component of the earth's magnetic field?
A
1
B
2
C
3
D
4
E
Q39
If the angle of declination in a place is 10°E, calculate the true geographic bearing if the compass reads N 40°E
A
N 50°E
B
40°E
C
N 30°E
D
25°E
E
Q40
The direction of the magnetic field at a point in the vicinity of a bar magnet is
A
always towards the north pole of a magnet
B
always away from the south pole of the magnet
C
along the line joining the point to the neutral point
D
in the direction the north pole of a compass needle would point
E
Q41
Which of the following is true of magnetism?
A
Iron fillings cling mainly round the ends of a bar magnet
B
The freely suspended bar magnet comes too rest in the geographic north-south direction
C
Like poles attract
D
Lodestone is a non-magnetic oxide
E
Q42
The angle between the magnetic meridian and the geographical meridian at a locality on the earth is the
A
longitude of the locality
B
angle of inclination at the locality
C
latitude of the locality
D
angle of declination of the locality
E
Q43
Which of the following is most strongly deflected by a magnetic field?
A
y-rays
B
&#945;-particles
C
&#946;-particles
D
X-rays
E
Q44
If the inclination at Ibadan is 7°S, this means that
A
the angle between the geographic meridian and the magnectic meridian at Ibadan is 7°
B
the earth's resultant magnetic intensity at Ibadan makes angle 7° with the horizontal direction
C
a magnetic needle will be inclined at 7° to the vertical at Ibadan
D
the north pole of a magnetic needle dips downwards at Ibadan
E
Q45

The diagrams below depict the current induced in a coil as a result of the relative motion between it and a bar magnet. Which of the diagrams illustrates the direction of the induced current?

A
B
C
D
E
Q46
Which of the following methods CANNOT be used to produce a steel magnet? The
A
passing of an electric current through a solenoid
B
repeated stroking of the specimen with a magnet
C
repeated stroking of the specimen in opposite directions with two magnets
D
heating of the specimen
E
hammering of the specimen in the earth's magnetic field
Q47
On which of the following does the operation of a moving coil ammeter depend ?       I. Electromagnetic induction      II. Force on a current-carrying conductor in a magnet field      III. Magnetic effect of an electric current
A
I only
B
II only
C
III only
D
II and III
E
I, II and III
Q48
Which of the following statements is NOT correct?
A
A galvanometer can be converted to an ammeter with a different range by connecting a high resistance in  series
B
An electric current always produces a magnetic field
C
Maxwell's screw rule states that if a corkscrew moves in the direction of the lines of force
D
Electromagnets are used in electric bells and telephone receivers
E
The lines of force round a straight current carrying conductor are circular
Q49
The electromotive force obtained from a simple dynamo may be increased by
A
increasing the cross-sectional area of the coil
B
winding the coil  on a soft-iron armature so as to decrease the magnetic flux through the coil
C
increasing the speed of rotation
D
making the field magnet longer
E
using low-resistance copper coils
Q50
A galvanometer of resistance 5.0 &#937; has full-scale deflection for  current of 100 mA . How would its range be extended to 1.0 A ? By placing a resistance of
A
5/9 &#937; in parrallel
B
9/5 &#937; in series
C
45 &#937; in parrallel
D
45 &#937; in series
E
9/5 &#937; in parallel
Q51
Fig 8 above represents an insulated cylindrical coil of copper wire wound round a paper tube. The ends of the coil are connected to a sensitive galvanometer. When a magnet was plunged into the coil, it was observed that the galvanometer needle gave a deflection. Which of the following statements correctly  describes this experiment
A
the effect illustrated is induced electromotive force
B
the strength of the current produced is inversely proportional to the speed with which the magnet is plunged into the coil
C
the direction of the current is always such as to enhance the charge producing it
D
the galvanometer gave a permanent deflection
E
on removing the magnet from the coil, the galvanometer deflected in the same direction.
Q52
A short bar magnetic is placed in the earth's magnetic field as shown in Fig 5. Which of the points I, II and III is (are) possible position(s) of a neutral point?
A
I only
B
II only
C
III only
D
I and II
E
I, II and III
Q53
The force with which an object is attracted to the earth is called its
A
acceleration
B
mass
C
gravity
D
impulse
E
weight
Q54
In Fig. 7 above, QR is a vertical conductor and the current, /, flows from R to Q. P is a point on the wire. The direction of the magnetic field at P due to the current is
A
Upward
B
north
C
south
D
west
E
east
Q55
Each of the diagrams in Fig. 6 represents two current carrying conductors situated close to each other. In which two diagrams are the forces between the two wires attractive?
A
I and V
B
I and III
C
II and IV
D
II and V
E
III and IV
Q56
As a positively charge rod is brought nearer to the top cap of a positively charged gold leaf electroscope , the divergence of the leaves will
A
decreases to zero
B
C
decrease to zero and the increase
D
remain constant
E
increase to a maximum and then decrease
Q57
A magnetic needle is suspended first at the earth's north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are
A
0° and 0°
B
60° and 60°
C
90° and 90°
D
90° and 0°
E
0° and 90°
Q58
The value if the series resistance required to convert the above galvanometer (Fig 9) into a voltmeter with a full range deflection of 15 V is
A
985 ohms
B
990 ohms
C
995 ohms
D
1, 000 ohms
E
1, 005ohms
Q59
Which of the following elements are real magnetic materials?
A
Iron, steel and nickel
B
Copper, steel and iron
C
D
E
Stone, air and iron
Q60
A closed coil wire is placed near a magnet. The magnet lies along the axis of the coil. Under which of the following conditions would there be no current in the coil?
A
When the coil is moved towards the stationary magnet
B
When the coil is moved away from the stationary magnet
C
When the coil is held staionary but the magnet is moved towards the coil
D
When both the coil and the magnet are held stationery
E
When the coil is held stationary but the magnet is moved away from the coil