JAMB UTME - Physics - 2020
Pregunta 1 Informe
A few grains of table salt were put in a cup of cold water, kept at constant temperature and left undistributed. Eventually all the water tested salty. This action is due to?
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Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration until they are evenly distributed. It occurs in various substances, such as gases, liquids, and solids, and is driven by the random motion of molecules. This process plays a crucial role in many biological and physical phenomena, such as the movement of oxygen and carbon dioxide across cell membranes, the dispersion of perfume in the air, and the mixing of solutes in solutions.
Pregunta 2 Informe
Two mirrors of the same length are arranges as show in the diagram. A ray of light NO strikes the system at O and emerges along PQ. The emergent ray has been deviated through
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| Angle of deviation = ?1+?2 = 50 + 50 + 40 + 40 |
| = 180o |
Pregunta 3 Informe
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A Mercury-in-glass thermometer works by measuring the expansion of mercury in a glass tube as the temperature increases. The lower fixed point is typically the point where the mercury is at its minimum and the upper fixed point is where the mercury is at its maximum. In this case, the lower fixed point is at 0°C and the upper fixed point is at 30°C, and the mercury is 210mm above the lower fixed point. So, the temperature of the room must be 30.43°C.
Pregunta 4 Informe
In what range of temperature is the expansion of water anomalous?
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Pregunta 5 Informe
Which of the following instruments consumes the highest current?
| I. Electric iron | 250v | 1kW |
| II. Television set | 220v | 110W |
| III. Torch light | 6v | 30W |
| IV.Immersion heater | 110v | 500W |
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Pregunta 6 Informe
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Pregunta 8 Informe
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Pregunta 9 Informe
In the figure, the value of R is
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| RT = V =12 = 6? |
| 1 2 |
| RT = 3 + R×6 |
| R+6 |
| R = 6Ω |
Pregunta 10 Informe
A hydrometer is an instrument for measuring the
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Pregunta 11 Informe
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The other options, 5.165cm and 5.0cm, may not be as accurate as they do not match up with the smallest increment that can be measured using vernier callipers.
Pregunta 12 Informe
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Pregunta 13 Informe
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Pregunta 14 Informe
The fiqure above represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40 , then the value of W is
Detalles de la respuesta
| V.E = 6, load = 120N |
| Efficiency = M.A x 1 x 100% |
| V.R |
| 40 = 120 x 1 x 100 |
| effort 6 1 |
| Effort = 50N |
Pregunta 15 Informe
Which of the following pairs is NOT part of the electromagnetic spectrum?
I. Radio waves
II. Beta rays
III. Gamma rays
IV. Alpha rays
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Pregunta 16 Informe
Which of the following statements about radioactivity is true?
(i) Alpha particle is positively charged
(ii) Beta particle is negatively charged
(iii) Gamma ray is neutral
(iv) Beta particle has the same mass as helium atom
(v) Gamma ray is charged.
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Pregunta 17 Informe
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Pregunta 18 Informe
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| Let N = count rate at zero time |
| N 3min→ N 3min→ N |
| 2 4 |
| N |
| 4 |
| 400 |
| N = 400 x N |
| N/4 |
| N = 1600 |
Pregunta 19 Informe
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Pregunta 20 Informe
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Pregunta 21 Informe
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Radioactivity is the spontaneous emission of radiation from atomic nuclei. This radiation can consist of alpha, beta, and gamma radiation.
Natural radioactivity is a purely nuclear phenomenon. The nucleus of a radioactive substance is unstable and such an unstable nucleus undergoes spontaneous breakdown (disintegration). The process continues until a stable nucleus is obtained.
Pregunta 22 Informe
A convex mirror is used as a driving mirror because
I. its image is erect
II. It has a large field of view
III. It has a long focal length
Identify the CORRECT statement(s)
Detalles de la respuesta
| A) RT = 2 + 3 + 6 = 11Ω |
| (B) RT = 3×3 = 1.2Ω |
| 2+3 |
| (C) RT = 3×2×6 |
| (2×3)+(2×6)+(3×6) |
| = 1Ω |
| (D) RT = 3 + 2×6 |
| 2+6 |
| = 4.5 Ω |
Pregunta 23 Informe
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Difference in time = 1 sec
Echo time = 1 / 2 = 0.5 sec
Difference of cliff from ship = 0.5 x 250
= 125m
Pregunta 24 Informe
Which of the following statements about defects of vision is/are CORRECT?
I. For a long sighted person, close objects appear blurred
II. For a short sighted person, distant objects appear blurred
III. Short sight is corrected by using a pair of converging lenses
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Pregunta 25 Informe
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| 3 x α = V2−V1 |
| V1×Δθ |
| 3 x 2 x 10−5 = V2−10 |
| 100×10 |
| V2 = (100 x 10 x 3 x 2 10−2) + 10 |
| = 10.6 cm3 |
Pregunta 26 Informe
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Pregunta 27 Informe
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| Heat energy = Electrical Energy |
| Hence, |
| MCθ = power x time |
| 5 x 1 x 10−2 x C = 100 x 20 |
| C = 200 |
| 5×102 |
| = 4 x 104 J/kg/oC |
Pregunta 28 Informe
In an experiment in which molten naphtha-line is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80 0c is known as the
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Pregunta 29 Informe
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Pregunta 30 Informe
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Pregunta 31 Informe
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| MaVa = MbVb |
| 5 x Va = 0.05 x 100 |
| Va = 1m−1 |
Pregunta 32 Informe
Consider the three forces acting at O and in equilibrium as shown in the figure. Which of the following equations is/are CORRECT?
I. \(P_1 \sin \theta_1 = p_1 \cos \theta_2\)
II. \(P_3 = P_1 \cos \theta_4 + P_2 \cos_2\)
III. \(P_1 \sin \theta_1 = p_2 \sin \theta_2\)
Detalles de la respuesta
From ?ABC
P = P1 cos ? From ACD
|
Pregunta 33 Informe
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Pregunta 34 Informe
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Pregunta 35 Informe
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P = (5 x 50) + (100 x 4)
= 650watts
Energy(kWhr) = 650 x 10-3 x 10
= 6.5 kWhr
1kWhr cost 2 kobo ; 6.5 kWhr will cost 2×6.512×6.51
= 13 kobo
Pregunta 36 Informe
Which of the following conditions are necessary and sufficient for total internal reflection to take place at the boundary between two optical media?
I. Light is passing from optical denser medium to optically less dense medium
II. Light is passing from optically less dense medium to optically denser medium to optically denser medium
III. Angle of incidence is greater
IV. Angle of incidence is lesser
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Pregunta 37 Informe
The effect of closing the key K in the circuit shown in the figure above would be to?
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| When K is open, the total Resistance = 8 + 2 = 10? |
| 1 = V? = 6v? = 0.6A |
| When K is closed, 18+18=1? |
| 28=1? |
| ? = 82 = 4? |
| ? = 82 = 4? |
| 4? in series with 2?= 6? |
| 1 = V? = 66 = 1A |
| 1 - 0.6A = 0.4A |
| Hence, 0.4A increase |
Pregunta 38 Informe
