JAMB Physics questions and answers 2021. This article will show 2021 JAMB Physics questions and answers, how JAMB Physics questions are set, and how to answer them.
It is a proven fact that JAMB questions are mainly picked from past questions and some examples and exercises in the JAMB recommended textbooks.
To score high in the JAMB Physics examination, read JAMB recommended textbooks on Physics and also do not forget to practise JAMB Physics past questions. See JAMB Form.
There are 40 question in the JAMB Physics questions and you are expected to attempt all the questions.
JAMB Questions and Answers on Physics 2021
Bear it in mind that JAMB questions are of types. So, do not expect to see exactly the same questions and answers for all the question paper types.
The JAMB Physics questions and answers on this page have been thoroughly explained in case your question papers does not match this one. The questions will be similar but different options and answers.
The steps for all the calculations are the same for related questions. Study this page intensively till you enter hall for your examination.
1. A man walks 1km due east and then due north. His displacement is
A. √2km N 45 degrees E
B. √1km N 30 degrees E
C. √1km N 15 degrees E
D. √2km N 60 degrees E
Explanation: Draw four cardinal points and label it N, E, S, and W and draw a horizontal line 1km (not to scale) due east and 1km due north. Join the line from the top to the bottom as shown in the diagram below:
R^2 = 1^2 + 1^2
R = √(1+1)
R = √2
Solving for tita implies
tan^-1(1/1) = 45 degree.
2. The density of the oil was 0.9 gcm^-3 before frying. If the density was 0.6 gcm^-3 after frying, assuming no loss of oil due to spilling, its new volume was
A. 360 cm^3
B. 600 cm^3
C. 240 cm^3
D. 800 cm^3
Explanation: Since there was no loss of oil due to spilling, Density x Volume = constant
D1V1 = D2V2
0.9V1 = 0.6V2
V2 = 0.9 x 400/0.6
V2 = 600 cm^3
3. Which of the following is true of an electrical charge?
A. Positive charge means deficit electrons
B. Negative charge means excess of electrons
C. Electric current means movement of electrons
D. All of the above.
4. Natural radioactivity consists of the emission of
A. alpha particles and beta rays
B. alpha particles and X-rays
C. alpha, beta rays, and gamma rays
D. gamma rays and X-rays
5. Which of the following does NOT describe the image formed by a plane mirror?
B. Laterally inverted
C. Same distance from mirror as object
6. What is the resultant resistance of the circuit given above?
A. 8 ohms
B. 11 ohms
C. 4 ohms
D. 3.6 ohms
Explanation: Calculate for the two resistors in parallel and then calculate For the series connection.
Formula for resistor in parallel, 1/ R = 1/R1 + 1/R2…
Formula for resistor in series, R = R1 + R2
The two resistors in parallel = 2 ohms and 2 ohms
this implies: 1/R = 1/2 + 1/2 = 1
R = 1 ohm
This 1 ohm resistor becomes in series with the 3 ohms and 4 ohms resistors
The resultant resistor of the circuit, Reqv. = 3+1+4 = 8 ohms.
7. Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?
B. Heat->Kinetic->Electricity->Heat and Light
8. Cathode rays are
A. High energy electromagnetic waves
D. streams of electrons
9. A narrow beam of white light can be split up into different colours by a glass prism. The correct explanation is that
A. white light is an electromagnetic wave
B. the prism has all the colours of the white light
C. different colours of white light travel with different speeds in glass
D. white light has undergone total internal reflection in the prism
10. The figure 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 percent, then the value of W is?
Explanation: Note that the velocity ratio, V.R = the number of blocks = 6
efficiency = M.A x 1/V.R X100
where M.A = mechanical advantage
Load = 120N
efficiency = 40
M.A = Load/effort
40 = 120/effort x 1/6 x 100/1
effort = 50N
11. What type of reaction is represented by the following scheme 21X + 21Y + 32Z + 10n +energy
A. Fusion reaction
B. Fission reaction
C. Chain reaction
D. Radioactive decay
12. The amount of heat needed to raise the temperature of 10kg of copper by 1K is its
A. specific heat capacity
B. latent heat
C. heat capacity
D. internal energy
13. The electrochemical equivalent of silver is 0.0012g/C. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5.0 minutes, the current must be
A. 6000 A
B. 100 A
C. 10 A
D. 1 A
Explanation: M = ZIt
I = M/Zt = 36/3x60x0.0012 = 100A
14. Shadows and eclipses result from the
A. refraction of light
B. reflection of light
C. defraction of light
D. rectilinear propagation of light
15. Which of the following obeys Ohm’s Law?
A. All metals
B. Diode only
C. All electrolytes
16. Which of the following statements are TRUE of isotopes? I. Isotopes of an element have the same chemical properties because they have the same number of electrons. II. Isotopes of elements are normally separated using physical properties. III. Isotopes of an element have the same number of protons in their nuclei.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
17. In the diagram above, the hanging mass m2 is adjusted until m1 is onthe verge of sliding. The coefficient of static friction between the mass m1 and the table is
Explanation: Recall m2g = um1g
where u = coefficient of static friction
u = m2/m1
18. Which of the following may be used to explain a mirage? I. Layers of air near the road surface have varying refractive indices in hot weather. II. Road surfaces sometimes become good reflectors in hot weather. III. Light from the sky can be reflected upwards after coming close to the road surface.
A. I and III only
B. II and III only
C. II only
D. I, II and III
19. In the diagram above, if the atmospheric pressure is 760mm, the pressure in the chamber G is
Explanation: 760+100 = Pg+30
pg = 830mm.
20. Which of the following has the lowest internal resistance when new?
A. Leclanche cell
B. Daniel cell
C. Torch battery
21. The pitch of an acoustic device can be increased by
A. decreasing the loudness
B. increasing the amplitude
C. increasing the frequency
D. decreasing the intensity
22. One of the features of fission process is that
A. it leads to chain reaction
B. its products are not radioactive
C. neutrons are not released
D. the sum of the masses of the reactants equals the sum of the masses of the products.
23. The linear expansivity of brass is 2 x 10^-5 C^-1. If the sum of the volume of a piece of brass is 15.00cm^3 at 0 degrees celsius. What is the volume at 100 degree celsius?
Explanation: Linear expansivity = V2-V1/V1 x difference in temperature
Note: volume or cubic expansivity = 3 x linear expansivity
3 x 2 x 10^-5 = V2 – 15/15(1100-0)
V2 = 15.09cm^3
24. A lead bullet of mass 0.05 kg is fired with a velocity of 200 m/s into a lead block of mass 0.95 kg. Given that the lead block can move freely, the final kinetic energy after impact is
A. 150 J
B. 100 J
C. 50 J
D. 200 J
Explanation: Since the collision is inelastic, the block and the bullet will move with common velocity after collision.
m1u1+m2u2 = (m1+m2)V
where V = common velocity
V = (m1u1+m2u2)/m1+m2
V= (0.05 x 200 + 0.95 x 0)/0.05+0.95
V = 10m/s
K.E = 1/2MV^2 = 1/2 (0.05+0.95) x10^2 = 50 J
25. In a series R-L-C circuit at resonance, the voltages across the resistor and inductor are 30 V and 40 V respectively. What is the voltage across the capacitor?
A. 30 V
B. 70 V
C. 50 V
D. 40 V
26. If the fraction of the atoms of a radioactive material left after 120 years is 1/6. What is the half of the material?
A. 20 years
B. 10 years
C. 2 years
D. 24 years
Explanation: Half life = Total time/stages
27. In the above diagram above, which of the simple pendulum will resonate with P when set into oscillation?
C. R and T
D. O and R
28. The time rate of loss of heat by a body is proportional to the
A. temperature of the body
B. difference of the body
C. difference in temperature between the body and its surroundings
D. ratio of the temperature of the body to that of its surroundings
29. A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X in place. When the finger is removed, the result is that Y has
A. no charge and a zero potential
B. a positive charge and a zero potential
C. a negative charge and a positive potential
D. a negative charge and a negative potential
30. Electrical appliances in homes are normally earthed so that
A. a person touching the appliances is safe from electric shock.
B. both the a.c and d.c sources can be used.
C. the appliances are maintained at a higher p.d. than the earth.
D. appliances are maintained at lower p.d. than the earth.
The process whereby a liquid turns spontaneously into vapour is called
32. Which of the following diagrams above represents correctly an n-p-n transistor?
33. The difference observed in solids ,liquids and gases may be accounted for by
A. Their relative masses
B. Their melting point
C. The spaces and forces acting between the molecules
D. The different molecules in each of them.
34. Convex mirrors are used as driving mirrors because images formed are
A. erect, virtual and diminished
B. erect, real and diminished
C. erect, virtual and magnified
D. inverted, virtual and diminished
35. Musical instruements playing the same note can be distinguished from one another owing to the difference in their
36. In the diagram above, if the south-poles of two magnets stroke a steel bar, the polarities at T and V will respectively be
A. north and south
B. south and south
C. north and north
D. south and north
37. In homes, electrical appliances and lamps are connected in parallel because
A. less current will be used
B. less voltage will be used
C. parallel connections does not heat up the wires
D. series connection uses high voltage
38. An object moves in a circular part of radius 0.5m with a speed of 1 m/s. What is its angular velocity?
A. 8 rad/s
B. 4 rad/s
C. 1 rad/s
D. 2 rad/s
Explanation: W = V/V = 1/0.5
39. What effort will a machine of efficiency 90% apply to lift a load of 180N if its efforts arm is twice as long as its load arm?
Explanation: M.A = Effort x V.R/100 = 90 X 2/100 = 1.8
40. Calculate the effective capacitance of the circuit above.
Explanation: For capacitors in parallel
C = C1 +C2 +C3 = 2+2+2 = 6 uf
Note :The 6uf capacitors become in series with the 2uf and 3uf capacitors
For capacitors in series 1/C = 1/C1 + 1/C2 + 1/C3 = 1/6 + 1/3 + 1/2 = 1+2+3/6 = 6/6 =1 i.e C =1uf
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