JAMB UTME - Physics - 2011
Ibeere 1 Ìròyìn
In an A.C circuit, the ratio of r.m.s value to peak value of current is
Awọn alaye Idahun
| Irms = | I0 |
| ?2 | |
| Therefore | ?2Irms | = | I0 |
| Irms | = | 1 | |
| I0 | ?2 |
Ibeere 2 Ìròyìn
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
Awọn alaye Idahun
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
Ibeere 3 Ìròyìn
In homes, electrical appliances and lamps are connected in parallel because
Awọn alaye Idahun
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.
Ibeere 4 Ìròyìn
The ground is always cold at night because the
Awọn alaye Idahun
The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground
Ibeere 5 Ìròyìn
A man standing on a lift that is descending does not feel any weight because
Awọn alaye Idahun
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
Ibeere 7 Ìròyìn
If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?
Awọn alaye Idahun
S = (1)/2gt2
S = (1)/2 x (10)/1 x 32 =5 x 9 = 45 m
Ibeere 8 Ìròyìn
If the threshold frequency for tungsten is 1.3 x 1015Hz, what is its work function?
[H = 6.6 x 10-34 Js]
Awọn alaye Idahun
Work function, w = hfo 6.6 x 10-34 x 1.3 x 1015
= 8.58 x 10-19
Ibeere 9 Ìròyìn
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?
Awọn alaye Idahun
Pressure in liquid is independent of cross sectional area of the container/ liquid
∴ the correct options are I & II
Ibeere 10 Ìròyìn
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?
Awọn alaye Idahun
Efficiency = work outputwork input×1001
= 40 = 20×10x×1001
= 500J
Ibeere 11 Ìròyìn
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?
Awọn alaye Idahun
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
Ibeere 12 Ìròyìn
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?
Awọn alaye Idahun
Heat supplied = Heat gained
P x t = C ∆ Ø
(25 x 5 x 60)/300 = 750 JK-1
Ibeere 13 Ìròyìn
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]
Awọn alaye Idahun
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
Ibeere 14 Ìròyìn
A metal of volume 40 cm3 is heated from 30 °c to 90 °c, the increase in volume is
Awọn alaye Idahun
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
Ibeere 15 Ìròyìn
Which of the following materials has an increase in resistance with temperature?
Awọn alaye Idahun
Resistance in metals are proportional to temperature
Ibeere 16 Ìròyìn
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?
Awọn alaye Idahun
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
Ibeere 17 Ìròyìn
Which of the following electromagnetic waves has the highest frequency?
Awọn alaye Idahun
r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves
Ibeere 18 Ìròyìn
The diagram above shows two vectors at right angles to each other. The value of the resultant vector is
Awọn alaye Idahun
The resultant, R is given by pythagoras rule, R2 = P2 + Q2
= 62 + 82 = 36 + 64 = 100
R = √100 = 10.0N
Ibeere 19 Ìròyìn
A radioactive isotope has a decay constant of 10-5s4. Calculate half life
Awọn alaye Idahun
T (1)/2 = (0.693)/λ = (0.693)/10-5
= 0.693 x 105
= 6.93 x 104 sec
Ibeere 21 Ìròyìn
Under which of the following conditions do gases conduct electricity?
Awọn alaye Idahun
Under high potential difference and low pressure gases are good conductor of electricity
Ibeere 22 Ìròyìn
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
Ibeere 23 Ìròyìn
When the human eye loses its power of accomodation, the defect is known as
Awọn alaye Idahun
presbyopia is loss of accommodation
Ibeere 24 Ìròyìn
The eclipse of the sun occurs when the
Awọn alaye Idahun
Eclipse of the sun occurs when the moon which is opaque objects between the sun and the earth
Ibeere 25 Ìròyìn
Which of the following will be applied when a metal Y is used to electroplate another metal X in electrolysis?
Awọn alaye Idahun
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
Ibeere 26 Ìròyìn
The correct expression for the potential at a point distance r from a charge q in an electric field is
Awọn alaye Idahun
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 |
Ibeere 27 Ìròyìn
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?
Ibeere 28 Ìròyìn
Steam burn is more severe than that of boiling water because
Awọn alaye Idahun
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
Ibeere 29 Ìròyìn
When a red rose flower is observed in blue light, what colour does the observer see?
Awọn alaye Idahun
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.
Ibeere 30 Ìròyìn
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]
Awọn alaye Idahun
upthrust = weight in air - weight in liquid = 30 x 10 - 22 x 10 = 300 - 220 = 80 N
Ibeere 31 Ìròyìn
Which of the following could be effectively used to reduce friction?
Awọn alaye Idahun
grease is more viscous than the rest of the liquids
Ibeere 32 Ìròyìn
The diagram above show the positions of a cone. The position which can be described as neutral equilibrium is represented as
Awọn alaye Idahun
Under neutral equilibrium, the body rolls and the position of the center of gravity , C. G is neither raised nor lowered
Ibeere 33 Ìròyìn
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
Ibeere 34 Ìròyìn
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?
Awọn alaye Idahun
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.
Ibeere 35 Ìròyìn
A perfect emitter or absorber of radiant energy is a
Awọn alaye Idahun
Dull, black surface are good emitters or absorbers of energy
Ibeere 36 Ìròyìn
Which of the following types of waves needs a medium for propagation?
Awọn alaye Idahun
Sound is the only mechanical wave among the rest which are electromagnetic waves.
Ibeere 37 Ìròyìn
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?
Awọn alaye Idahun
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
Ibeere 38 Ìròyìn
I. change of state
II. Diffusion
III. Radiation
IV. Osmosis
Which of the processes above can be explained using the kinetic theory?
Awọn alaye Idahun
Ibeere 39 Ìròyìn
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]
Awọn alaye Idahun
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
Ibeere 40 Ìròyìn
The phenomenon that shows that increase in pressure lowers the melting point can be observed in
Awọn alaye Idahun
Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.
Ibeere 43 Ìròyìn
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
Awọn alaye Idahun
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
Ibeere 44 Ìròyìn
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
Awọn alaye Idahun
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.
Ibeere 45 Ìròyìn
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]
Awọn alaye Idahun
V = (2X)/t
330 = (2 x 4.95 x 103)/t
t = (9.9. x 103/330 = (9900)/330 = (90)/3
= 30 secs
Ibeere 46 Ìròyìn
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
Awọn alaye Idahun
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
Ibeere 47 Ìròyìn
If the volume of a gas increases steadily as the temperature decreases at constant pressure, the gas obeys
Awọn alaye Idahun
Ibeere 48 Ìròyìn
If a tube of small radius opened at both ends is placed in a liquid, the liquid will
Awọn alaye Idahun
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
Ibeere 49 Ìròyìn
Which of the following is a property of steel?
Awọn alaye Idahun
Steel is not easily magnetized and dismagnetized
Ibeere 50 Ìròyìn
The electrical properties of germanium can be altered drastically by the addition of impurity. This process is referred to as
Awọn alaye Idahun
