Q7652.A $3000 \mathrm{W}$ electric cooker is to be used on a $200 \mathrm{V}$ mains circuit. Which of the fuses below can be used safely with the cooker?
A$2 \mathrm{A}$
B$5 \mathrm{A}$
C$10 \mathrm{A}$
D$20 \mathrm{A}$
Correct Answer: D
$I = \dfrac{P}{V} = \dfrac{3000}{200} = 15 \mathrm{A}$. A $20 \mathrm{A}$ fuse is safe.
JAMB (UTME)
Physics
1994
Q7653.A galvanometer has a resistance of $5 \Omega$. By using a shunt wire of resistance $0.05 \Omega$, the galvanometer could be converted to an ammeter capable of reading $2 \mathrm{A}$. What is the current through the galvanometer?
Q7654.In the diagram above, if the internal resistance of the cell is zero, the ratio of the power $P_1$ and $P_2$ dissipated by $R_1$ and $R_2$ respectively, is
A$\dfrac{R_2}{R_1}$
B$\dfrac{R_1}{R_2}$
C$\dfrac{R_1 + R_2}{R_2}$
D$\dfrac{R_1 + R_2}{R_1}$
Correct Answer: A
In parallel, $P = \dfrac{V^2}{R}$, so $P \propto \dfrac{1}{R}$. $\dfrac{P_1}{P_2} = \dfrac{R_2}{R_1}$.
JAMB (UTME)
Physics
1994
Q7655.If $\Delta x$ is the uncertainty in the measurement of the position of a particle along the x-axis and $\Delta P_x$ is the uncertainty in the measurement of the linear momentum along the x-axis, then the uncertainty principle relation is given as
A$\Delta x \Delta P_x > h$
B$\Delta x \Delta P_x = 0$
C$\Delta x \Delta P_x < h$
D$\Delta x \Delta P_x \geq \dfrac{h}{4\pi}$
Correct Answer: D
Heisenberg's uncertainty principle: $\Delta x \Delta P_x \geq \dfrac{h}{4\pi}$.
JAMB (UTME)
Physics
1994
Q7656.$^{23}_{11}\mathrm{Na} + \text{Proton} \rightarrow X + \text{alpha particle}$. What are the values of p and q respectively in the equation above?
A$10$ and $20$
B$12$ and $24$
C$20$ and $10$
D$24$ and $12$.
Correct Answer: C
$^{23}_{11}\mathrm{Na} + ^1_1\mathrm{H} \rightarrow ^A_Z\mathrm{X} + ^4_2\mathrm{He}$. Mass: $23 + 1 = A + 4 \Rightarrow A = 20$. Atomic: $11 + 1 = Z + 2 \Rightarrow Z = 10$. So X is $^{20}_{10}\mathrm{X}$.
JAMB (UTME)
Physics
1994
Q7657.A semi-conductor diode is used in rectifying alternating current into direct current mainly because it
AAllows current to flow in either direction
BIs non-linear
COffers a high input resistance
DAllows current to flow only in one direction.
Correct Answer: D
A diode conducts in one direction only.
JAMB (UTME)
Physics
1994
Q7658.In semi-conductors, the carriers of current at room temperature are
AElectrons only
BElectrons and holes
CHoles only
DElectrons and ions
Correct Answer: B
In semiconductors, current is carried by both electrons and holes.
JAMB (UTME)
Physics
1994
Q7659.What is the speed of a particle of mass $10^{-7} \mathrm{kg}$ whose wavelength is $10^{-8} \mathrm{m}$?
A$6.63 \mathrm{ms}^{-1}$
B$66.30 \mathrm{ms}^{-1}$
C$663.00 \mathrm{ms}^{-1}$
D$6630.00 \mathrm{ms}^{-1}$
Correct Answer: A
$\lambda = \dfrac{h}{mv}$. $v = \dfrac{h}{m\lambda} = \dfrac{6.63 \times 10^{-34}}{10^{-7} \times 10^{-8}} = \dfrac{6.63 \times 10^{-34}}{10^{-15}} = 6.63 \times 10^{-19} \mathrm{ms}^{-1}$. The answer key A is incorrect.
JAMB (UTME)
Physics
1994
Q7660.In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are $30 \mathrm{V}$ and $40 \mathrm{V}$ respectively. What is the voltage across the capacitor?
A$30 \mathrm{V}$
B$40 \mathrm{V}$
C$50 \mathrm{V}$
D$70 \mathrm{V}$
Correct Answer: B
At resonance, $V_C = V_L = 40 \mathrm{V}$.
JAMB (UTME)
Physics
1994
Q7661.Gamma rays are produced when
AHigh velocity electrons are abruptly stopped in metals
BEnergy changes occur within the nucleus of atoms
CEnergy changes occur within the electronic structure of atoms
DElectrons are deflected in very strong magnetic fields.
Correct Answer: B
Gamma rays are produced by energy changes within the nucleus.
JAMB (UTME)
Physics
1994
Q7662.In the Rutherford scattering experiment, a beam of alpha particles was fired at a thin gold film with some of the particles being considerably deflected. This shows that
AA gold nucleus contains protons, neutrons and electrons uniformly distributed in a tiny volume.
BThe gold nucleus is positively charged and is concentrated in a tiny volume.
CThe gold nucleus emitted alpha particles
DThe gold nucleus is concentrated in a tiny volume and contains alpha particles.
Correct Answer: B
The deflection of alpha particles shows that the nucleus is positively charged and concentrated in a tiny volume.
JAMB (UTME)
Physics
1994
Q7663.A catapult used to hold a stone of mass $500 \mathrm{g}$ is extended by $20 \mathrm{cm}$ with an applied force F. If the stone leaves with a velocity of $40 \mathrm{ms}^{-1}$, the value of F is
A$4.0 \times 10^4 \mathrm{N}$
B$4.0 \times 10^3 \mathrm{N}$
C$2.0 \times 10^3 \mathrm{N}$
D$4.0 \times 10^2 \mathrm{N}$
Correct Answer: C
$W = \dfrac{1}{2}Fx = \dfrac{1}{2}mv^2$. $F = \dfrac{mv^2}{x} = \dfrac{0.5 \times 40^2}{0.2} = \dfrac{0.5 \times 1600}{0.2} = 4000 \mathrm{N}$. The answer key C is incorrect; the correct answer is B ($4.0 \times 10^3 \mathrm{N}$).
Instruction
JAMB Physics 1995
JAMB (UTME)
Physics
1995
Q7664.A body of mass $4 \mathrm{kg}$ is acted on by a constant force of $12 \mathrm{N}$ for $3 \mathrm{s}$. The kinetic energy gained by the body at the end of the time is
Q7665.As the pressure of a fluid increases, its viscosity
ADecreases
BRemains constant
CIncreases then decreases
DIncreases.
Correct Answer: D
For liquids, viscosity generally increases with pressure.
JAMB (UTME)
Physics
1995
Q7666.I. Jet-propelled aircraft
AI, II, III and IV
BI and III only
CI and II only
DI, II and III only
Correct Answer: A
All the listed phenomena are based on Newton's third law of motion.
JAMB (UTME)
Physics
1995
Q7667.In a hydraulic press, a force of $40 \mathrm{N}$ is applied on the effort piston of area $0.4 \mathrm{m}^2$. If the force exerted on the load piston is $400 \mathrm{N}$, the area of the large piston is
Q7668.A $100 \mathrm{kg}$ box is pushed along a road with a force of $500 \mathrm{N}$. If the box moves with a uniform velocity, the coefficient of friction between the box and the road is $[g = 10 \mathrm{ms}^{-2}]$
Q7669.The earth is four times the size of the moon and the acceleration due to gravity on the earth is $80$ times that on the moon. The ratio of the mass of the moon to that of the earth is
Q7670.The diagram above shows forces $4 \mathrm{N}$, $6 \mathrm{N}$, $10 \mathrm{N}$ and $8 \mathrm{N}$ which act at a point O in directions indicated. The net horizontal force is
Q7671.A radioisotope has a decay constant of $10^{-7} \mathrm{s}^{-1}$. The average life of the radioisotope is
A$6.93 \times 10^8 \mathrm{s}$
B$1.00 \times 10^{-7} \mathrm{s}$
C$1.00 \times 10^7 \mathrm{s}$
D$6.93 \times 10^7 \mathrm{s}$
Correct Answer: C
Average life $\tau = \dfrac{1}{\lambda} = \dfrac{1}{10^{-7}} = 1.00 \times 10^7 \mathrm{s}$.
JAMB (UTME)
Physics
1995
Q7672.A moving-coil galvanometer has a full-scale deflection of $3 \mathrm{A}$ equivalent to $30^{\circ}$ deflection. The sensitivity of the instrument is
A$10.0$
B$33.0$
C$90.0$
D$0.1$
Correct Answer: D
Sensitivity $= \dfrac{\text{deflection}}{\text{current}} = \dfrac{30}{3} = 10 \mathrm{degree/A}$. The answer key D is incorrect; the correct answer is A.
JAMB (UTME)
Physics
1995
Q7673.The binding energy of helium $^4_2\mathrm{He}$ is
A$2.017 \mathrm{U}$
B$0.033 \mathrm{U}$
C$4.033 \mathrm{U}$
D$0.330 \mathrm{U}$
Correct Answer: B
Mass defect $= 2(1.00783) + 2(1.00867) - 4.0026 = 2.01566 + 2.01734 - 4.0026 = 0.0304 \mathrm{U}$. The closest answer is B.
JAMB (UTME)
Physics
1995
Q7674.In a tuned radio receiver R, L, C series circuit for resonance, the inductive and capacitive reactance $X_L$ and $X_C$ respectively are related as
A$X_L = X_C$
B$X_L = \dfrac{1}{X_C}$
C$X_L = 2X_C$
D$X_L = \dfrac{1}{2}X_C$
Correct Answer: A
At resonance, $X_L = X_C$.
JAMB (UTME)
Physics
1995
Q7675.The particle and wave nature of matter are demonstrated in the equation
A$\lambda = \dfrac{h}{p}$
B$\lambda = \dfrac{p}{h}$
C$\lambda = hp$
D$\lambda = \dfrac{h}{p^2}$
Correct Answer: A
de Broglie equation: $\lambda = \dfrac{h}{p}$.
JAMB (UTME)
Physics
1995
Q7676.For semiconductors to have negative temperature coefficient of resistance implies that
AThey have electrons and holes at high temperatures
BTheir resistance is constantly changing with temperature
CTheir resistance increases with temperature
DTheir resistance decreases with temperature.
Correct Answer: D
Negative temperature coefficient means resistance decreases as temperature increases.
JAMB (UTME)
Physics
1995
Q7677.Fluorescent tubes produce light by the
ARefraction of light by gas molecules
BExcitation of gas molecules
CConduction of solar energy
DThermal agitation of electrons in the tube.
Correct Answer: B
Fluorescent tubes produce light by excitation of gas molecules.
JAMB (UTME)
Physics
1995
Q7678.In a reverse biased junction diode, current flows in by
AElectrons alone
BMajority carriers
CMinority carriers
DPositive holes alone
Correct Answer: C
In reverse bias, current is due to minority carriers.
JAMB (UTME)
Physics
1995
Q7679.The energy stored in an inductor of inductance $5 \mathrm{mH}$ when a current of $6 \mathrm{A}$ flows through it is
Q7680.X-rays can be used in the study of crystal structures because they
AHave an extremely short wavelength
BHave a very long wavelength
CAre very fast
DAre invisible.
Correct Answer: A
X-rays have wavelengths comparable to atomic spacing in crystals.
JAMB (UTME)
Physics
1995
Q7681.An a.c. circuit of e.m.f. $12 \mathrm{V}$ has a resistor of resistance $8 \Omega$ connected in series to an inductor of inductive reactance $16 \Omega$ and a capacitor of capacitive reactance $10 \Omega$. The current flow in the circuit is
Q7682.A generator-manufacturing company was contracted to produce an a.c. dynamo but inadvertently produced a d.c. dynamo. To correct this error, the
ACommutator should be replaced with slip rings.
BCommutator should be replaced with slit rings.
CArmature coil should be made of aluminium.
DArmature coil should be made of silver.
Correct Answer: A
Replacing the commutator with slip rings converts a d.c. dynamo to an a.c. dynamo.
JAMB (UTME)
Physics
1995
Q7683.Transverse waves can be distinguished from longitudinal waves using the characteristic of
ADiffraction
BPolarization
CReflection
DRefraction.
Correct Answer: B
Polarization is a property of transverse waves only.
JAMB (UTME)
Physics
1995
Q7684.When left in a freezer, a bottle full of water cracks on freezing into ice because of the
ADecrease in the volume of water
BContraction of the bottle
CExpansion of the bottle
DIncrease in the volume of water
Correct Answer: D
Water expands when it freezes, causing the bottle to crack.
JAMB (UTME)
Physics
1995
Q7685.The change in volume when $450 \mathrm{kg}$ of ice is completely melted is
A$0.05 \mathrm{m}^3$
B$0.45 \mathrm{m}^3$
C$4.50 \mathrm{m}^3$
D$0.50 \mathrm{m}^3$
Correct Answer: A
Volume of ice $= \dfrac{450}{900} = 0.5 \mathrm{m}^3$. Volume of water $= \dfrac{450}{1000} = 0.45 \mathrm{m}^3$. Change $= 0.5 - 0.45 = 0.05 \mathrm{m}^3$.
JAMB (UTME)
Physics
1995
Q7686.If a force of $50 \mathrm{N}$ stretches a wire from $20 \mathrm{m}$ to $20.01 \mathrm{m}$, what is the amount of force required to stretch the same material from $20 \mathrm{m}$ to $20.05 \mathrm{m}$?
Q7687.Tea pots are often silver-coated to prevent heat loss by
AConvection and conduction
BRadiation only
CConduction only
DConvection only.
Correct Answer: B
Silver coating reduces heat loss by radiation.
JAMB (UTME)
Physics
1995
Q7688.The phase difference between waves P and Q in the diagram above is
A$\dfrac{\pi}{2}$
B$2\pi$
C$\dfrac{\pi}{4}$
D$\pi$
Correct Answer: D
The waves are out of phase by half a cycle, which is $\pi$ radians.
JAMB (UTME)
Physics
1995
Q7689.Metal rods of length $20 \mathrm{cm}$ each are laid end to end to form a bridge at $25^{\circ}\mathrm{C}$. What gap will be provided between consecutive rails for the bridge to withstand $75^{\circ}\mathrm{C}$? [Linear expansivity of steel $= 1.2 \times 10^{-5} \mathrm{K}^{-1}$]
A$0.012 \mathrm{cm}$
B$0.024 \mathrm{cm}$
C$0.12 \mathrm{cm}$
D$0.24 \mathrm{cm}$
Correct Answer: A
$\Delta L = L\alpha\Delta T = 20 \times 1.2 \times 10^{-5} \times 50 = 0.012 \mathrm{cm}$.
JAMB (UTME)
Physics
1995
Q7690.A $50 \mathrm{W}$ electric heater is used to heat a metal block of mass $5 \mathrm{kg}$. If in $10 \mathrm{minutes}$, a temperature rise of $12^{\circ}\mathrm{C}$ is achieved, the specific heat capacity of the metal is
Waves are characterized by wavelength, velocity, and frequency.
JAMB (UTME)
Physics
1995
Q7692.The instrument used for securing a large number of similar charges by induction is called
ACapacitor
BElectrophorus
CElectroscope
DProof-plane
Correct Answer: B
An electrophorus is used to produce a large number of similar charges by induction.
JAMB (UTME)
Physics
1995
Q7693.A steady current $2 \mathrm{A}$ flows in a coil of e.m.f. $12 \mathrm{V}$ for $0.4 \mathrm{s}$. A back e.m.f. of $3 \mathrm{V}$ was induced during this period. The stored energy in the loop that can be utilized is
A$7.2 \mathrm{J}$
B$12.0 \mathrm{J}$
C$2.4 \mathrm{J}$
D$9.6 \mathrm{J}$
Correct Answer: A
Net e.m.f. $= 12 - 3 = 9 \mathrm{V}$. Energy $= VIt = 9 \times 2 \times 0.4 = 7.2 \mathrm{J}$.
JAMB (UTME)
Physics
1995
Q7694.If $16 \mathrm{mA}$ of current flows through a conductor in one second, the number of electrons transported per second is