JAMB UTME - Physics - 2011
Tambaya 1 Rahoto
The electrical properties of germanium can be altered drastically by the addition of impurity. This process is referred to as
Bayanin Amsa
Tambaya 2 Rahoto
If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?
Bayanin Amsa
S = (1)/2gt2
S = (1)/2 x (10)/1 x 32 =5 x 9 = 45 m
Tambaya 3 Rahoto
The eclipse of the sun occurs when the
Bayanin Amsa
Eclipse of the sun occurs when the moon which is opaque objects between the sun and the earth
Tambaya 5 Rahoto
A copper wire was subjected to a tensile stress of 7.7 x 107 x 10 Nm-2. calculate strain of the wire.
[young modules = 1.1 x 1011 Nm-2]
Bayanin Amsa
Young modules = Tensile stressTensile strain
= 1.1×1011=7.7×107Tensile Strain
∴ Tensile strain = 7.7×1071.1×1011
= 7.0×107−11=7.0×10−4
Tambaya 6 Rahoto
Two balls X and Y weighing 5 g and 50 kg respectively were throne up vertically at the same time with a velocity of 100 ms1 .How will their positions be one second later?
Bayanin Amsa
v2 = U2 - 2G s
0 = 1002 - 2 x 10 x s = 10000 - 20s
s = (10000)/20 = 500m
Which is independent of mass.the two bodies where acted upon by the same retarding force of gravity which is independent of mass of the body; therefore both will be 500 m from the point of throw.
Tambaya 7 Rahoto
A certain far - sighted person cannot see object that are closer to the eye than 50 cm clearly. Determine the power of the converging lens which will enable him to see at 25 cm
Bayanin Amsa
V = - 50, U = 25CM
(1)/r = (1)/v + (1)/u = (1)/-50 + (1)/25 = (1 + 2)/50 = (1)/50 f = +50cm = +0.5m
p = (1)/r = (1)/0.5 = (10)/5 = 2 diopters
The power of a lens is the reciprocal of the focal length in meters. it is expressed in diopters.
Tambaya 8 Rahoto
Under which of the following conditions do gases conduct electricity?
Bayanin Amsa
Under high potential difference and low pressure gases are good conductor of electricity
Tambaya 9 Rahoto
A machine is used to lift a load of 20 N through a height of 10 m. if the efficiency of the machine is 40%, how much work is done?
Bayanin Amsa
Efficiency = work outputwork input×1001
= 40 = 20×10x×1001
= 500J
Tambaya 10 Rahoto
Which of the following electromagnetic waves has the highest frequency?
Bayanin Amsa
r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves
Tambaya 11 Rahoto
The bond between silicon and germanium is
Tambaya 12 Rahoto
A cannon is fired from town X,after how long is the sound heard at a town Y 4.95 km away?
[velocity of sound in the air = 330 ms-1]
Bayanin Amsa
V = (2X)/t
330 = (2 x 4.95 x 103)/t
t = (9.9. x 103/330 = (9900)/330 = (90)/3
= 30 secs
Tambaya 13 Rahoto
A perfect emitter or absorber of radiant energy is a
Bayanin Amsa
Dull, black surface are good emitters or absorbers of energy
Tambaya 14 Rahoto
A length of wire has a frequency of 255Hz when stretched by a force of b225N. If the fore increased to 324N, what is the new frequency of vibration
Bayanin Amsa
f1 = 255Hz, T1 = 225N
f2 = ? T2 = 324N
But f ∝ √T => f = K√T
=> K = f/√T
∴ f1/√T1 = f2/√T2225/√225 = f2/√324
| f2 = | 225√225 |
| √225 |
| = | 225 x 18 |
| __15 |
= 306Hz
Tambaya 15 Rahoto
A radioactive isotope has a decay constant of 10-5s4. Calculate half life
Bayanin Amsa
T (1)/2 = (0.693)/λ = (0.693)/10-5
= 0.693 x 105
= 6.93 x 104 sec
Tambaya 16 Rahoto
A carpenter on top of a roof of 20.0m high dropped a hammer of mass 1.5 kg and it fell directly to the ground. the kinetic energy of the hammer just before hitting the ground is?
[g = 10 ms-2]
Bayanin Amsa
K e just before hitting the gound
= P e at the maximum height (conservation of mechanical energy)
K e = P e = mgh = 1.5 x 10 x 20
= 300 J
Tambaya 17 Rahoto
Two resistors 5Ω and 10Ω are arranged first in series and later in parallel to a 24V source, the ratio of total power dissipated in the series and parallel arrangements respectively is
Bayanin Amsa
Tambaya 18 Rahoto
A metal of volume 40 cm3 is heated from 30 °c to 90 °c, the increase in volume is
Bayanin Amsa
increase in volume, DV = RV1 ∆ θ = 3α Vsub>1 Dθ
= 3 x 2.0 X 10-5 x 40 x (90 - 30)
= 6 x 10-5 x 40 x 60
0.144 cm3
∴ No correct option
Tambaya 19 Rahoto
Three similar cells each of e.m.f 2 v and internal resistance 2Ω are connected in parallel, the total e.m.f and total internal resistance are respectively
Bayanin Amsa
Total energy in parred connection is equal to emt of one cell, = 2v but total internal resistance is given by
(1)/r = (1)/r1 + (1)/r2 + (1)/r3 = (1)/2 + (1)/2 + (1)/2 = (3)/2
∴ r = (2)/3 = 0.67Ω
Tambaya 20 Rahoto
Which of the following will be applied when a metal Y is used to electroplate another metal X in electrolysis?
Bayanin Amsa
Metals and hydrogen are deposited at the cathode, while non-metals and oxygen are deposited on the anode
∴ metals Y will form the anode which is deposited at the cathode made of x
Tambaya 21 Rahoto
The diagram above show the positions of a cone. The position which can be described as neutral equilibrium is represented as
Bayanin Amsa
Under neutral equilibrium, the body rolls and the position of the center of gravity , C. G is neither raised nor lowered
Tambaya 22 Rahoto
If the volume of a gas increases steadily as the temperature decreases at constant pressure, the gas obeys
Bayanin Amsa
Tambaya 23 Rahoto
The capacitance of a parallel plate capacitor is 20 μf in air and 60 μf in the presence of a dielectric. What is the dielectric constant?
Bayanin Amsa
Dielectric constant = (c)/c° = (60)/20 = 3
Tambaya 24 Rahoto
I. Density of the liquid.
II. Depth below the surface of the liquid.
III. Surface area of the liquid.
In which of the statement above will pressure be dependent?
Bayanin Amsa
Pressure in liquid is independent of cross sectional area of the container/ liquid
∴ the correct options are I & II
Tambaya 25 Rahoto
Steam burn is more severe than that of boiling water because
Bayanin Amsa
The specific latent heat of vaporization of steam is 2.1 x 106JKg-1
while the energy required to raise the temperature of a unit mass of water from 0°c to 100°c = C x Dt = 4200 x 100 = 420000 = 4.2 x 105 JKg-1
? steam possesses greater heat energy per unit mass
Tambaya 26 Rahoto
The bond between silicon and germanium is
Tambaya 27 Rahoto
In an A.C circuit, the ratio of r.m.s value to peak value of current is
Bayanin Amsa
| Irms = | I0 |
| ?2 | |
| Therefore | ?2Irms | = | I0 |
| Irms | = | 1 | |
| I0 | ?2 |
Tambaya 28 Rahoto
The correct expression for the potential at a point distance r from a charge q in an electric field is
Bayanin Amsa
Electric potential is work done in taking a unit mass or charge from infinity to that point
| V = | w | = | Fr | = | Q1Q2 | x | r |
| Q | Q | 4πεor2 | Q1 |
| = | _q |
| 4πεor |
Tambaya 29 Rahoto
Which of the following types of waves needs a medium for propagation?
Bayanin Amsa
Sound is the only mechanical wave among the rest which are electromagnetic waves.
Tambaya 30 Rahoto
Which of the following could be effectively used to reduce friction?
Bayanin Amsa
grease is more viscous than the rest of the liquids
Tambaya 31 Rahoto
An object of mass 2 kg moves with a velocity of 10 ms1 round at circle of radius 4 m. Calculate the centripetal force on the object
Bayanin Amsa
Centripetal force,
F = mv2r
= 2×1024
= 2004
= 50N
Tambaya 32 Rahoto
The phenomenon that shows that increase in pressure lowers the melting point can be observed in
Bayanin Amsa
Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.
Tambaya 33 Rahoto
An image in a convex lens is upright and magnified 3 times. If the focal length of the lens is 15 cm, what is the object distance?
Bayanin Amsa
m = v/u = -3
v = -3u
f = 15cm
1/v + 1/U = 1/f1/-3U + 1/u = 1/152/3u = 1/15
3U = 15 x 2
U = 30/3
= 10 cm
Tambaya 34 Rahoto
A man standing on a lift that is descending does not feel any weight because
Bayanin Amsa
The resultant force acting on the man is given by w = mg - R
Mg - mg = 0
The man feels weightless because the reaction, R is equal to the weight mg
Tambaya 35 Rahoto
Two inductors of inductance 4 II and 8 II are arrange in series and a current of 10 A is passed through them. What is the energy stored in them?
Bayanin Amsa
Effective inductance
(1)/L = (1)/4 + (1)/8 = (3)/8
∴ L = (8)/3
Energy stored = (1)/2 LI2
= (1)/2 x (8)/3 x 10 x 10 = (400)/3 = 133.3 J
Tambaya 36 Rahoto
When a red rose flower is observed in blue light, what colour does the observer see?
Bayanin Amsa
The colour which an object presents to the eye is the colour of light it reflects. Red rose flower will therefore absorb any other colour and reflect red. Therefore when viewed in blue light, it has no colur to reflect and will therefore appear black. Although mixture of red light and blue light = magenta . NO correct option.
Tambaya 37 Rahoto
When the human eye loses its power of accomodation, the defect is known as
Bayanin Amsa
presbyopia is loss of accommodation
Tambaya 38 Rahoto
I. change of state
II. Diffusion
III. Radiation
IV. Osmosis
Which of the processes above can be explained using the kinetic theory?
Bayanin Amsa
Tambaya 39 Rahoto
If a tube of small radius opened at both ends is placed in a liquid, the liquid will
Bayanin Amsa
The liquid will rise up the capillary if it wets glass and falls below its wets glass and falls below its initial level if it does not wet glass
Tambaya 40 Rahoto
The ground is always cold at night because the
Bayanin Amsa
The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground
Tambaya 41 Rahoto
I. High thermal capacity.
II. High sensitivity.
III.Easy readability.
IV. Accuracy over a wide range of temperature
From the statement above, the qualities of a good thermometer are
Bayanin Amsa
A good thermometric liquid should not have a high thermal capacity so that the themperetue of the body being measured will not be affected
? II, III and IV are qualities of a good thermometer
Tambaya 42 Rahoto
If the threshold frequency for tungsten is 1.3 x 1015Hz, what is its work function?
[H = 6.6 x 10-34 Js]
Bayanin Amsa
Work function, w = hfo 6.6 x 10-34 x 1.3 x 1015
= 8.58 x 10-19
Tambaya 43 Rahoto
An object weighs 22 kg in water and 30kg in air. what is the upthrust exerted by the liquid on the object.
[g = 10 ms2]
Bayanin Amsa
upthrust = weight in air - weight in liquid = 30 x 10 - 22 x 10 = 300 - 220 = 80 N
Tambaya 44 Rahoto
The diagram above shows two vectors at right angles to each other. The value of the resultant vector is
Bayanin Amsa
The resultant, R is given by pythagoras rule, R2 = P2 + Q2
= 62 + 82 = 36 + 64 = 100
R = √100 = 10.0N
Tambaya 45 Rahoto
Which of the following is a property of steel?
Bayanin Amsa
Steel is not easily magnetized and dismagnetized
Tambaya 46 Rahoto
Which of the following materials has an increase in resistance with temperature?
Bayanin Amsa
Resistance in metals are proportional to temperature
Tambaya 47 Rahoto
If the charge of electricity is K wh is N4, what is the cost of operating an electrical appliance rated 250 v,2 A for six hours?
Bayanin Amsa
Energy consumed = power x time = lvt = 2 x 250 x 6hr = 300 wh = 3 kwh but 1 kwh = N4
3 kwh = 3 x N4 = N 12
Tambaya 48 Rahoto
A block of aluminum is heated electrically by a 25 W heater. if the temperature rises by 10°C in 5 minutes, the heat capacity of the aluminum is?
Bayanin Amsa
Heat supplied = Heat gained
P x t = C ∆ Ø
(25 x 5 x 60)/300 = 750 JK-1
Tambaya 49 Rahoto
In homes, electrical appliances and lamps are connected in parallel because
Bayanin Amsa
The voltage of a circuit is the same whether in parallel or in series. Parallel and series affects resistance and current. So the answer should be it uses less current.
