A transformer is rated 240v. If the primary coil is 4000 turns and the secondary voltage 12v, determine the number of turns in the secondary coil.
- A. 200
- B. 100
- C. 250
- D. 150
the ray which causes gas molecules to glow is known as
- A. cathode ray
- B. anode ray
- C. molecular ray
- D. gamma ray
the ray which causes gas molecules to glow is known as
- A. cathode ray
- B. anode ray
- C. molecular ray
- D. gamma ray
The charge carriers in gasses are
- A. ions only
- B. electrons and ions
- C. electrons and holes
- D. electrons only
A silicon material is dopped with an element of a certain group and an n-type semi-conductor is formed. the most likely group of the element is
- A. V
- B. III
- C. I
- D. II
When impurities are added to semi-conductors, the conductivity of the semi-conductor
- A. increases then decreases
- B. increases
- C. decreases
- D. remains constant
a proton moving with a speed of 1.0 x 106ms-1 through a magnetic field of 1.0T experiences a magnetic force of magnitude 8.0 x 10-14 N. The angle between the proton”s velocity and the field is
- A. 60°
- B. 90°
- C. 30°
- D. 45°
the time it will take a certain radioactive material with a half-life of 50 days to reduce to 1/32of its original number is
- A. 250days
- B. 150days
- C. 300days
- D. 200days
In an a.c circuit that contains only a capacitor, the voltage lags behind the current by
- A. 180°
- B. 90°
- C. 60°
- D. 30°
An object is projected for the hieght of 80 m above the ground with a velocity of 40ms-1 at the angle of 30° to the horizontal. The time of flight
- A. 8 s
- B. 4 s
- C. 16 s
- D. 10 s
In an ideal wheel an axle system, R stand for the radius of the wheel and r is the radius of the axle. the mechanical advantage is
- A. (R/r)2
- B. r/R
- C. (r/R)2
- D. R/r
The pair of physical quantities consisting of vectors only are
- A. momentum and power
- B. velocity and distance
- C. displacement and torque
- D. accelaration and speed
A real image three times the size of an object is formed 24cm from a converging mirror. what is the focal length of the mirror.
- A. 16cm
- B. 6cm
- C. 8cm
- D. 12cm
A thin converging lens has a power of 4.0 diopters determined its focal length.
- A. 2.50m
- B. 0.03m
- C. 5.00m
- D. 0.25m
The sharpness of the boundary of the shadow of an object is determined by the
- A. intensity of light striking the object
- B. rays of light passing through the object
- C. nature of the object
- D. opacity of the object
Marching soldiers crossing a suspension bridge are usually advised to break their steps to avoid damaging the bridge owing to
- A. oscillation
- B. resonance
- C. swinging
- D. vibration
A man exerts a pressure of 2.8 x 103Nm-2 on the ground and has 4 x 10-2m2 of his feet in contact with the ground. The weight of the man is
- A. 102N
- B. 70N
- C. 140N
- D. 112N
Transverse waves can be distinguished from longitudinal waves using the characteristic of
- A. diffraction
- B. refraction
- C. polarization
- D. reflection
Metal rods of length 20m each are laid end to end to form a bridge at 25oC. What gap will be provided between consecutive rails for the bridge to withstand 75oC?
[Linear expansivity of the material = 2.0 x 10-5K-1
- A. 0.20m
- B. 0.22m
- C. 0.25m
- D. 0.02m
A 50W electric heater is used to heat a metal block of mass 5kg. If in 10 minutes a temperature rise of 12oC is achieved, the specific heat capacity of the metal is
- A. 400 J kg-1K-1
- B. 500 J kg-1K-1
- C. 390 J kg-1K-1
- D. 130 J kg-1K-1
I. Wavelength
II. Medium of propagation
III. Wave velocity
IV. Frequency
V. Energy
Which of the above are used for characterizing waves?
- A. I, II and V
- B. I and IV
- C. I, III and IV
- D. III, IV and V