cameroon gce intermediate level 2024 electrical machines 1

cameroon gce intermediate level 2024 electrical machines 1

cameroon gce intermediate level 2024 electrical machines 1

The unit of magnetic flux density is
A Weber
B Ampere turn
C Ampere turn meter
D Wcbcr/mcter square
2. The number of lines of force produced by a
magnetic source is called
A magnetic flux density
B magnetic flux
C magnetic field strength
D magneto motive force
9. Sclf–inductancc occurs when
A The circuit is charging
B The resistance is changing
C The flux is changing
3. A transformer has a turn ratio of 10:1. If the D The current is changing
primary has a current of 100mA, how much
current flows in the secondary?
A 0.1A
B 1A
C 10A
D 0.01A
10. Short circuit test of a transformer helps us to find
A Copper loss at no load
B Copper loss at any desired load
C Iron loss
D Full–load Cu loss
4. The total flux in the core of an electrical machine
is 20mWb and its flux density is IT. Calculate the
cross–sectional area of the core.
A A = 0.02m2
B A = 0.05m2
C A = 20m2
D A = 50m2
11. The emf equation of a transformer of secondary
turns N2, magnetic flux density Bm, magnetic
area of core a, and operating at frequency f is
given by:
A E2=4.44N2Bmaf Volts
E2=4.44
C E2= MmL volts
D E2=1.11 N2Bmaf Volts
B N 2 Bmf Volts
5. There is a force of attraction between tw‘o current
carrying conductors when the current in them is
A Of different magnitude
B In the same direction
C In opposite direction
D Of the same magnitude
12. A short circuit test and an open circuit test carried
on a single phase transformer gave a power of
500W and 400W respectively. What will be the
total losses of the transformer to obtain maximum
efficiency?
A 900W
B 400W
C 800W
D 500W
6. The emf induced in a coil of inductance 12H by a
current changing at a rate of 4 A/S is
A –48V
B 12V
C 3V
D 4V 13. An advantage of an auto–transformer over a
double w‘ound ratio is that:
A It gives high step–up ratio
B Iron losses are reduced
C Copper loss is reduced
D It reduces capacitance between turns
7. An 8H inductor has a current of 3A flowing
through it. How much energy is stored in the
magnetic field of the inductor?
A 72 joules
B 36 joules
C 24 joules
D 3 joules