All 40 questions from the Joint Admissions and Matriculation Board (JAMB) Physics 2017 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
Advertisement
A waterfall is 42m high. Calculate the difference in temperature of the water between the top and bottom of the waterfall, assuming no heat is lost. [specific heat capacity of water = 4.20x10³ Jkg⁻¹K⁻¹, g=10ms⁻²]
Potential energy converts to heat energy: mgh = mcΔθ, so Δθ = gh/c = (10x42)/4200 = 0.1°C.
A body when slightly displaced is said to be in neutral equilibrium only if it tends to
In neutral equilibrium, a body comes to rest in a new position with its centre of gravity and height unchanged.
A string of length 5m is extended by 0.04m when a load of 0.8kg is suspended at the end. How far will it extend if a force of 16N is applied? [g=10ms⁻²]
Weight=mg=8N gives F=Ke, K=8/0.04=200Nm⁻¹. For F=16N, e=16/200=0.08m.
Which of the following has negligible mass?
Gamma rays are electromagnetic radiation (photons) and have no rest mass, unlike alpha/beta particles or protons.
How can energy loss be minimized through Eddy-current?
Using laminated, insulated soft iron cores reduces eddy current loss by limiting induced current paths.
Calculate the upthrust on an object of volume 50cm³ which is immersed in liquid of density 10³kgm⁻³. [g=10ms⁻²]
Upthrust U=ρVg = 10³ x (50x10⁻⁶) x 10 = 0.5N.
Which of the following would appear when a white screen is illuminated by red and green light?
Red and green primary colours of light combine to produce the secondary colour yellow.
I. Refraction II. Interference III. Diffraction. Which of the above properties are common to all waves?
Refraction, interference and diffraction are all properties common to all wave types.
Calculate the electric field intensity between two plates of potential difference 6.5V separated by a distance of 35cm.
E=V/d = 6.5/0.35 = 18.57NC⁻¹.
The distance between the image and the object in a plane mirror is 40cm. If the distance of the object from the mirror is reduced by 9.2cm, what is the new distance of the object from the mirror?
Object distance u=20cm (half of 40cm). New object distance = 20-9.2 = 10.8cm; the image distance equals this, giving new total separation. [Values in cm; consistent with the worked solution logic.]
Find the potential energy of an object of mass 10kg placed on a building floor 10m above the ground level. [g=10ms⁻²]
PE = mgh = 10x10x10 = 1,000J.
The volume of a fixed mass of gas is 10cm³ when its pressure is 400cmHg. Determine the volume of the gas when its pressure is 200cmHg.
Boyle's Law: P1V1=P2V2. 400x10=200xV2, so V2=20cm³.
The product PV, where P is pressure and V is volume, has the same unit as
Pressure x Volume = (N/m²)x(m³) = Nm = Joule, the unit of work.
What is the cost of running seven 40W lamps and five 80W lamps for 12 hours if the electrical energy cost is N7.00kWhr?
Total power = 7x40+5x80 = 280+400 = 680W = 0.68kW. Energy = 0.68x12 = 8.16kWh. Cost = 8.16x7 = N57.12.
The thermal expansion of a solid is an advantage in
Thermal expansion (contraction on cooling) is deliberately used to fit metal tyres tightly onto wheels.
Calculate the specific latent heat of vaporization of steam if 1.13x10⁶J of heat energy is required to convert 15kg of it to water.
L = Q/m = 1.13x10⁶/15 = 7.53x10⁴Jkg⁻¹ (using Q=1.13x10⁶J, m=15kg).
A stationary wave pattern is formed by a wave of frequency 40Hz and velocity 60cms⁻¹. What is the distance between adjacent nodes?
λ=v/f=60/40=1.5cm; distance between adjacent nodes = λ/2 = 0.75cm.
Calculate the height of the image formed by a pinhole camera of length 12cm used to photograph an object 60cm away from the hole and 70cm high.
Image height/object height = image distance/object distance: hi/70 = 12/60, hi = 14cm.
From the diagram, calculate the energy stored in the capacitor (8μF capacitor, 10V supply).
Energy = ½CV² = ½x8x10⁻⁶x10² = 4.0x10⁻⁴J.
Which of the following is a scalar quantity?
Mass has magnitude only (no direction), making it a scalar quantity, unlike tension, weight and impulse which are vectors.
Calculate the time taken for a mango fruit that fell from the tree 20m to the ground. [g=10ms⁻²]
s=½gt²: 20=½x10xt², t²=4, t=2s.
Which of the following instruments is most appropriate in the measurement of the thickness of a piece of paper?
The micrometer screw gauge measures very small thicknesses precisely, such as a sheet of paper.
What is the energy of a radiation that has the frequency of 8.2x10¹⁶Hz? [h=6.63x10⁻³⁴Js]
E=hf = 6.63x10⁻³⁴ x 8.2x10¹⁶ = 5.44x10⁻¹⁷J.
Under what conditions are cathode rays produced in a discharge tube?
Cathode rays are produced in a discharge tube under low pressure and high voltage.
Why do soldiers march disorderly while crossing a bridge?
Breaking marching step prevents resonance, which could otherwise build up and collapse the bridge.
In a pure inductive and capacitive circuit, where is all the energy stored when the current is at the peak?
When current is at peak (maximum), all the energy is stored in the magnetic field of the inductor.
Calculate the voltage across a 5μF capacitor connected to an ac source of frequency 50/πHz when a current of 0.25A flows through the circuit.
Xc=1/(2πfC)=1/(2x50x5x10⁻⁶)=2000Ω; V=IXc=0.25x2000=500V.
If silicon is doped with phosphorous, what type of semiconductor material will be formed?
Doping silicon (tetravalent) with phosphorus (pentavalent) creates excess electrons, forming n-type semiconductor material.
A block and tackle pulley arrangement has 6 pulleys, in which an effort of 50N supports a load of 200N. Calculate the efficiency of the machine.
V.R = number of pulleys = 6; M.A = Load/Effort = 200/50 = 4. Efficiency = M.A/V.R x100% = 4/6x100 = 66.7%.
Which of the following is an advantage of a thermoelectric thermometer? It is
A thermoelectric thermometer (thermocouple) is very sensitive to small temperature changes.
Determine the focal length of a converging lens if the power is 5.0 dioptres.
f=1/P=1/5=0.2m.
Which of the following statements about magnetism is true?
A freely suspended magnet aligns itself along the Earth's magnetic field, roughly north-south.
Calculate the force on a 5m long wire carrying a current of 8A and lying in a direction at 30° to a magnetic field of magnetic flux density 0.6T.
F=BILsinθ = 0.6x8x5xsin30° = 24x0.5 = 12N.
Which of the following is correct about an electric cell?
Secondary (rechargeable) cells have very low internal resistance, allowing them to deliver large currents, unlike primary cells.
From the diagram (18Ω, 12Ω and 6Ω resistors in parallel, connected to a 12V source), calculate the total current in the circuit.
1/R = 1/18+1/12+1/6 = 11/36, R≈3.27Ω. I=V/R=12/3.27≈3.7A.
Calculate the angle of minimum deviation of a 60° prism of refractive index 1.5. [sin⁻¹0.75=49°]
Using n=sin((A+Dm)/2)/sin(A/2), solving gives Dm ≈ 38.00°.
Which of the following statements is NOT correct? Molecules of a liquid or stationary gas are made up of...
Molecules of a liquid are NOT stationary — they are in constant, random motion, making option A the incorrect (and thus correct-answer) statement.
Which of the following is NOT part of the electromagnetic spectrum?
Alpha particles are charged particles (helium nuclei), not electromagnetic radiation, unlike gamma rays, infrared and radio waves.
The diagram shows a circuit with a 1A ammeter and a voltmeter, and a diode. It shows the application of the diode in
The single-diode circuit shown represents half-wave rectification.
Which of the following instructions helps maintain the correct humidity and temperature of a building?
An air conditioner regulates both temperature and humidity of a building.
Advertisement
…and/or go further with premium services and No Ads.