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WorksheetsWilliams End of Month Exercise
Total questions: 74
Worksheet time: 2hrs 1mins
__________ magnets never lose their magnetism.
Natural
Induced
Permanent
Artificial
How does the compass works?
It is attracted by a lodestone's magnetic field
It is attracted by The Earths magnetic field
It is attracted by a lodstone magnetic field
It is attracted by The Earth's magnetic field
The strongest parts of the magnet are ...
fronts
backs
poles
middle
What would happen is a north pole of a magnet came close to a north pole of another magnet?
they would be attracted to each other
they would be repelled from each other
What would happen with the magnets in the picture above?
They would repel
Nothing
They would attract
They would repel and then attract
Can you produce current in a wire with a magnet that is sitting still?
Yes; having a magnet near a wire is enough to excite the electrons
No; the magnetic field has to be changing to excite the electrons
No; magnets cannot create electricity
A coil spins in a magnetic field. Of the following
which causes an increase in the induced EMF in
the coil?
Spinning the coil faster
Removing the coil from the magnetic field
Keeping the flux at a constant rate
Decreasing the number of turns of wire in
the coil
Magnetic flux is related to magnetic field strength by the formula
Φ=BA
Φ=BA2
Φ=B/A
Φ=B/A2
When a charged particle moving with velocity v enters a magnetic field at right angles it will be forced into a circular path with radius r given by
mv/Bq
Bq/mv
mv2/Bq
none of these
The size of the force exerted on a moving charge relative to an external magnetic field is given by
Bqv
Bqvcosθ
Bqvsinθ
none of these
A uniform magnetic field of strength 4 mT is used to deflect a beam of electrons into a circular path of diameter 65 mm. Calculate the speed of the electrons
2.3x107ms-1
4.6x107ms-1
3.0x107ms-1
2.0x107ms-1
What does the direction of the pointing fingers mean in this picture?
the direction of the voltage
the rotation of the wire
the direction of the magnetic field
the direction of the current
F = BIL If the current and magnetic field are doubled, the magnetic force on the wire
halves
remains the same
doubles
quadruples
F = qvB If the speed and charge double, what happens to the magnetic force?
halves
remains the same
doubles
quadruples
A uniform magnetic field its intensity is 3x10-3 T pass an
area of coil with 100 turns which makes 60 angle with the coil. What is the area of the coil if the magnetic flux is 0.15 Wb?
0 m2
0.5 m2
0.57 m2
1 m2
A wave that can only travel through matter is called:
solid waves
longitudinal waves
transverse waves
mechanical waves
True or false: In Transverse waves particles travel side to side in a wave.
true
false
A wave that can travel through matter and empty space is a:
electromagnetic wave
longitudinal wavy
transverse wave
mechanical
The winding of wire around a core which is connected to a source of energy is called the ....... coil.
primary
secondary
tertiary
Calculate potential difference in the secondary coil based on the information given below.
Vp = 240 V
Np = 20
Ns = 125
Vs ?
1500
500
1000
2000
Why transformers work with A.C. current but not D.C.
A.C current produces changing magnetic field.
D.C current produces changing magnetic field.
D.C current is weak
A.C current is powerful
A transformer has 100 turns in the primary coil and 25 turns in the secondary coil. When a 120 V is applied to the primary coil, what is the voltage in the secondary coil?
480V
30V
20V
450V
Transformer is always connected to ___________ supply.
A.C.
D.C.
For increasing the voltage ___________ is used.
Step up transformer
Step down transformer
Current transformer
A transformer has primary voltage 200V and secondary voltage 100V , the transformer is called _______ .
Step up
Step Down
None
Electrical symbol of a TRANSFORMER
The value of the second winding voltage of an iron-core transformer depends upon the ....... of turns, this winding contains as compared to the number of ........ winding turns.
primary, size
number, primary
size, height
number, size
Why might a current-carrying wire be placed between a magnetic field?
To increase the current from the interaction of magnetic fields
To increase the voltage from the interaction of magnetic fields
To produce a force from the interaction of magnetic fields
What angle must there be between a magnetic field and a conductor in order for the maximum force to be exerted?
180
45
90
270
Name one factor that does not affect the size of a force in on a current-carrying conductor placed in a magnetic field?
Gravity
Magnetic flux density/size of magnetic field
Size of the current
Length of the conductor
A 20 cm section of wire with a current of 8 A is at 90 degrees to a 0.1 T magnetic field. What direction is the force and calculate the size of it? F = BIl
up, 0.1 x 8 A x 20 cm = 16 N
down, 0.1 x 8 A x 20 cm = 16 N
down, 0.1 x 8 A x 0.20 m = 0.16 N
up, 0.1 x 8 A x 0.20 m = 0.16 N
Which rule can be used to work out which way a coil of wire rotates in a motor?
Fleming's left-hand rule
Fleming's right-hand rule
Give two ways you can reverse the direction of a basic dc motor?
Reverse the current
Keep the current the same
Reverse the magnetic field
Keep the magnetic field the same
How does a split ring commutator work?
Swaps the contact evert full turn, so that the left-hand and right-hand arms of the coil always experience a force in the same direction.
Swaps the contact evert half turn, so that the left-hand and right-hand arms of the coil do not experience a force in the same direction.
Swaps the contact evert half turn, so that the left-hand and right-hand arms of the coil always experience a force in the same direction.
What connects the current source with the commutator of a motor.
brushes
armature
magnet
commutator
Device that uses electromagnetic induction to change the voltage of electric current.
thermometer
galvanometer
electric transformer
electric motor
The primary coil of a transformer has 10 loops and 1,200V. The secondary coil has a voltage of 2,400 V, what is the number of loops in this coil?
2
20
10
25
