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Physics
WAEC / WASSCE 2017
Electromagnetic Field
Solution
A transformer connected to a 240\(V_{r.m.s}\) has 3000 turns in its primary coil and 500 turns in its secondary coil. Calculate the output voltage.
A
4000V
B
400V
C
40V
D
4V
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2010
Electromagnetic Field
Solution
Power supply is transmitted at a very high voltage and low current in order to?
A
make pass through the trasformers
B
increase the power supply
C
make it travel fast
D
prevent overheating of the coil
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2008
Electromagnetic Field
Solution
A step-down transformer has a power output of 50 W and efficiency of 80%. if the mains supply voltage is 200 v, calculate the primary current of the transformer.
A
0.31 A
B
3.20 A
C
3.40 A
D
5.00 A
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2008
Electromagnetic Field
Diagram
Solution
Given the inductor of inductance 5mH, 10mH and 20mH connected in series, the effective inductance is
A
0.35mH
B
3.50mH
C
2.90mH
D
35.0mH
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2004
Electromagnetic Field
Solution
A generator manufacturing company was contracted to produce an a.c dynamo but inadvertently produced a d.c dynamo. To correct this error, the
A
armature coil should be made of silver
B
commutator should be replaced with slip ring
C
commutator should be replaced with split rings
D
armature coil should be made of aluminium
medium Difficulty
Study Explanation
Physics
WAEC / WASSCE 2003
Electromagnetic Field
Solution
The direction of induced current in a straight wire placed in magnetic field is determined by using?
A
Fleming's right hand rule
B
Maxwell's screw rule
C
Faraday's law
D
Lenz's law
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2002
Electromagnetic Field
Solution
Which of the following statements is true of the properties of a moving coil galvanometer?
A
THe coil has a small area
B
There are strong hair springs to gives a large control panlel
C
There is a strong permanent magnet to give high magnetic flux
D
it has a small number of turns of coil
medium Difficulty
Study Explanation
Physics
UTME / JAMB 2000
Electromagnetic Field
Diagram
Solution
If current flows in the direction of the arrows in the solenoid above, the north pole is at
A
P
B
Y
C
X
D
Q
medium Difficulty
Study Explanation
Physics
UTME / JAMB 1992
Electromagnetic Field
Diagram
Solution
PQRS is rectangular cell with PQ perpendicular to the magnetic field as shown above. If a current flows in the the direction PQRS in what direction will the coil move
A
Upwards
B
Downwards
C
TOwards The North Pole
D
Towards The South Pole
medium Difficulty
Study Explanation
Physics
WAEC / WASSCE 1991
Electromagnetic Field
Solution
An induction coil is generally used to?
A
rectify an alternating current
B
produce a large input voltage
C
smoothen a pulsating direct current
D
modulate an incoming signal
E
produce a large output voltage
medium Difficulty
Study Explanation
Physics
WAEC / WASSCE 1988
Electromagnetic Field
Solution
What is the effect of using split-rings in a simple d.c motor?
A
The direction of rotation of the coil is reversed
B
The current in the coil flows in the same direction
C
The current in the coil becomes alternating
D
The direction of the force on the coil is reversed
E
The contact with the voltage is cut-off
medium Difficulty
Study Explanation
Physics
UTME / JAMB 1987
Electromagnetic Field
Solution
When a transformer has more secondary windings than primary windings, it?
A
has a smaller secondary current
B
has a greater power output
C
is a step-down transformer
D
increases the total energy output
medium Difficulty
Study Explanation