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Question 1 Report
The correct expression for the potential at a point distance r from a charge q in an electric field is
Answer Details
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 |
Question 2 Report
The bond between silicon and germanium is
Question 3 Report
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?
Answer Details
Efficiency = work outputwork input×1001 $\frac{\text{work output}}{\text{work input}}\times \frac{100}{1}$
= 40 = 20×10x×1001
$\frac{20\times 10}{x}\times \frac{100}{1}$
= 500J
Question 4 Report
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
Question 5 Report
Steam burn is more severe than that of boiling water because
Answer Details
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
Question 6 Report
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]
Answer Details
Young modules = Tensile stressTensile strain $\frac{\text{Tensile stress}}{\text{Tensile strain}}$
= 1.1×1011=7.7×107Tensile Strain $1.1\times {10}^{1}1=\frac{7.7\times {10}^{7}}{\text{Tensile Strain}}$
∴ Tensile strain = 7.7×1071.1×1011 $\frac{7.7\times {10}^{7}}{1.1\times {10}^{1}1}$
= 7.0×107−11=7.0×10−4
Question 7 Report
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?
Answer Details
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
Question 8 Report
In homes, electrical appliances and lamps are connected in parallel because
Answer Details
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.
Question 9 Report
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
Answer Details
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
Question 10 Report
A metal of volume 40 cm3 is heated from 30 °c to 90 °c, the increase in volume is
Answer Details
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
Question 11 Report
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]
Answer Details
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
Question 12 Report
A perfect emitter or absorber of radiant energy is a
Answer Details
Dull, black surface are good emitters or absorbers of energy
Question 13 Report
In an A.C circuit, the ratio of r.m.s value to peak value of current is
Answer Details
Irms = | I_{0} |
?2 | |
Therefore | ?2Irms | = | I_{0} |
Irms | = | 1 | |
I_{0} | ?2 |
Question 14 Report
The diagram above shows two vectors at right angles to each other. The value of the resultant vector is
Answer Details
The resultant, R is given by pythagoras rule, R2 = P2 + Q2
= 62 + 82 = 36 + 64 = 100
R = √100 = 10.0N
Question 15 Report
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
Answer Details
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.
Question 16 Report
If the threshold frequency for tungsten is 1.3 x 1015Hz, what is its work function?
[H = 6.6 x 10-34 Js]
Answer Details
Work function, w = hfo 6.6 x 10-34 x 1.3 x 1015
= 8.58 x 10-19
Question 17 Report
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?
Answer Details
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.
Question 18 Report
The electrical properties of germanium can be altered drastically by the addition of impurity. This process is referred to as
Question 19 Report
The eclipse of the sun occurs when the
Answer Details
Eclipse of the sun occurs when the moon which is opaque objects between the sun and the earth
Question 20 Report
Which of the following could be effectively used to reduce friction?
Answer Details
grease is more viscous than the rest of the liquids
Question 21 Report
If the volume of a gas increases steadily as the temperature decreases at constant pressure, the gas obeys
Question 22 Report
The bond between silicon and germanium is
Question 23 Report
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]
Answer Details
upthrust = weight in air - weight in liquid = 30 x 10 - 22 x 10 = 300 - 220 = 80 N
Question 24 Report
Under which of the following conditions do gases conduct electricity?
Answer Details
Under high potential difference and low pressure gases are good conductor of electricity
Question 25 Report
In the circuit above, three resistors, 2Ω, 4Ω and 12Ω are connected in parallel and a 12V battery is connected across the combination. The current flowing through the 12Ω resistors is
Answer Details
I | V |
R |
= | 12 |
12 |
Question 26 Report
Which of the following is a property of steel?
Answer Details
Steel is not easily magnetized and dismagnetized
Question 27 Report
If a tube of small radius opened at both ends is placed in a liquid, the liquid will
Answer Details
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
Question 28 Report
Which of the following types of waves needs a medium for propagation?
Answer Details
Sound is the only mechanical wave among the rest which are electromagnetic waves.
Question 29 Report
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?
Question 30 Report
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?
Answer Details
Pressure in liquid is independent of cross sectional area of the container/ liquid
∴ the correct options are I & II
Question 31 Report
A radioactive isotope has a decay constant of 10-5s4. Calculate half life
Answer Details
T (1)/2 = (0.693)/λ = (0.693)/10-5
= 0.693 x 105
= 6.93 x 104 sec
Question 32 Report
Which of the following materials has an increase in resistance with temperature?
Answer Details
Resistance in metals are proportional to temperature
Question 33 Report
Which of the following electromagnetic waves has the highest frequency?
Answer Details
r - rays has the highest frequency followed by X - rays, ultraviolet ray, visible light intra - red and the least is radio weaves
Question 34 Report
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]
Answer Details
V = (2X)/t
330 = (2 x 4.95 x 103)/t
t = (9.9. x 103/330 = (9900)/330 = (90)/3
= 30 secs
Question 35 Report
The diagram above show the positions of a cone. The position which can be described as neutral equilibrium is represented as
Answer Details
Under neutral equilibrium, the body rolls and the position of the center of gravity , C. G is neither raised nor lowered
Question 36 Report
The ground is always cold at night because the
Answer Details
The earth radiate heat to the atmosphere at night thereby lowering the temperature of the ground
Question 37 Report
I. change of state
II. Diffusion
III. Radiation
IV. Osmosis
Which of the processes above can be explained using the kinetic theory?
Question 38 Report
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?
Answer Details
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
Question 39 Report
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?
Answer Details
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
Question 40 Report
A man standing on a lift that is descending does not feel any weight because
Answer Details
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
Question 41 Report
If it takes an object 3s to fall freely to the ground from a certain height, what is the distance covered by the object?
Question 42 Report
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
Answer Details
Centripetal force,
F = mv2r
$\frac{m{v}^{2}}{r}$
= 2×1024
$\frac{2\times {10}^{2}}{4}$
= 2004
$\frac{200}{4}$= 50N
Question 43 Report
In measuring high frequency a.c, the instrument used is the
Answer Details
Hot wire ammeter is used because the heat affect of A C is same as that of DC
Question 44 Report
When the human eye loses its power of accomodation, the defect is known as
Answer Details
presbyopia is loss of accommodation
Question 45 Report
The phenomenon that shows that increase in pressure lowers the melting point can be observed in
Answer Details
Regelation means refreezing a phenomenon whereby melted ice free from increased pressure refreezed when they are released from the pressure.
Question 46 Report
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
Answer Details
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
Question 47 Report
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
Answer Details
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 |
Question 48 Report
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?
Answer Details
Heat supplied = Heat gained
P x t = C ∆ Ø
(25 x 5 x 60)/300 = 750 JK-1
Question 49 Report
Which of the following will be applied when a metal Y is used to electroplate another metal X in electrolysis?
Answer Details
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
Question 50 Report
When a red rose flower is observed in blue light, what colour does the observer see?
Answer Details
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.
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